Obsessed with someone & don't know what to do

I'm gonna apologize in advance because this is going to be really long, but I just need to get all this out because I don't have anyone in my life I can talk to this about and I just really need help with this. My family all loves me & stuff, but they wouldn't understand & some would be upset because of our religion (I'll explain this in detail later). I also don't even feel comfortable talking to a therapist about it because I can't even bring myself to say this all out loud. & I'm separating this into paragraphs to hopefully make it easier to read bc it will be long, but I need to just get it all out to someone, so please bear with me.

So, a little about me: I'm 18, I'm a girl & a senior in high school about to graduate. Ive always been straight & consider myself to be a Christian and so is my dad's side of the family (parents are divorced) but I've been struggling with being faithful lately because of this. I have been officially diagnosed with depression & severe anxiety, but I have all the symptoms of BPD and will be talking to my doctor about this.

There is this girl who was in one of my classes last semester (I'm on block schedule, so we get all new classes after Christmas) that's been somewhat of an acquaintance pretty much since I've been in school (my entire grade has all been together since elementary school). & Honestly I struggle with being paranoid, so I'm scared to give out too much info just in case for some reason she came across this & connected all the dots. Anyway, we started talking more bc we both didn't have many friends in there & we started being more like actual friends. At first she kinda annoyed me because we disagreed on political stuff (now I've completely changed sides, mostly because of her). & then later I started feeling almost attracted to her. This scared me because most Christian's believe being gay or bi or anything like that is wrong. Now I've never really supported it until recently, but I would not tolerate anyone bashing or being mean to people that are gay. They deserve the same respect & love as anyone else. Unfortunately my Christian side of the family feels the opposite. So I kinda pushed the feelings aside & went on and kinda forgot about it.

So it gets midway through the semester & the feelings come back, but way stronger. At first it was kinda just like a "girl crush" everybody talks about & you know crushes have this elated type feeling, but then a week later I was like "holy $#%^, I freaking love her & I want her so bad." So, she's not the girly girl type at all, but she's not like guyish (couldn't think of a better word to use) either. I kinda thought at one point, before I knew her well, she might've been bi or something, but then I figured she probably wasn't.

I started to get upset because I realized that there's a 99.9% chance we would never ever ever be a thing because 1) I thought she was more than likely into guys ( currently I'm not sure & I'll expand on that later) and 2) I'm not pretty. At all.
And I knew that it was wrong for me to feel like that for her, so I was also feeling extremely guilty.

So, I got severely depressed & for the first time ever in my life, I actually wanted to die. I prayed everyday for God to forgive me for what I was feeling, & I just didn't want to live like that anymore.

As I got to know her better, I learned she is kind of a drinker & she has this group of friends she does all that with, she was also into pills. Now at this point, I'd gotten so depressed I was taking 3mg of my parent's Xanax almost everyday just to make me feel okay. Then I wanted to drink to stop feeling anything, & also just to give me a reason to be around her. I planned to drink with her & another girl but it never went through. & I also stupidly gave her some of my pills because she wanted them & I was to the point where I was being reckless just to be around her & get her to like me more.

We hung out some at football games & I honestly look back on those & it hurts so bad because then I felt like she actually really liked me then (only as a friend). I feel like those were the happiest days I've had because I was around her & it was great. But then, she got close to this other girl that, from things I know about that happened, is a pretty terrible friend. But hey, there's also stuff I don't know.

So the semester starts ending & I got the feeling she didnt really like me that much anymore, and that hurt so bad I just wanted my life to be over. *note I'm not suicidal, actually scared of death, I just wanted life to peacefully be over. Then I switched from an anti-anxiety to an antidepressant because I was worrying my family because I wasn't eating & I was just so upset & almost heartbroken & they could tell. They'd ask why, but I'd say I couldn't tell them.

Then, the semester is in the last week & some stuff happened in my life and family & I kinda told her way more about that than I should (because she was like my person I wanted to tell everything to) so I worry that kinda made her not like me even more.
So Christmas break starts & she kept posting stories with this other friend(let's call her A) on Snapchat that I hate solely for the reason that A gets this girl's attention & I don't. & A was actually kinda mean to her about an argument that A took the wrong way.
*Let's call the girl I like X now so this doesn't get confusing.
So I just deleted X because I would see these Snapchat stories & break down in tears because I just wanted to be around X so bad because honestly I missed her so much, but then it was like I didn't exist and she was always with A.
So she snap chatted me one day & I didn't get it until after I set it to get snaps from anyone instead of just friends, & she had actually sent me one about something random & so she would've seen it was pending & knew I deleted her. So then she probably thought I didn't like her.
So second semester we had 1 class together, but it was like we were never friends bc we never talked, soI got out of the class because I was nervous & I was feeling all that pain all over again. I also made a new Snapchat & added her on it, but deleted her again bc I couldn't handle seeing the stories with A. I've also got my suspicions she may have a thing going on with A, but that's probably my paranoia & they're likely just close friends that are always together (like my & my best friend too I guess).

So fast forward to the present, about 6 months since I first had serious feelings for her & 3 since we last talked. After that class we got closer in was over, our friendship was over too pretty much. I learned to kinda push the feelings away & she was still on my mind a lot, just not as much.

Now here's my problem currently: we talked just the other day for the first time in a while bc of a school function (still got the vibe she doesn't like me that much, which hurts like everything) so it was a short awkward conversation bc I was just so desperate to talk to her. Now the feelings are back, and she's all I've thought about for the past 4 days. Literally my thoughts are on her from when I wake up to when I go to sleep. I even dream about her some nights.

I'm past the point of even feeling guilty about my feelings being wrong, I'm to the point where I would do almost anything to be with her. In a few months we'll graduate & move to 2 different schools across our state, and I'll probably never see her much ever again. That thought makes me physically sick.

I avoid her like the plague in the halls now because she makes me nervous because I worry so much about what she thinks about me and I don't want her to suspect I feel anything for her. I don't even know how to define my sexuality anymore because I'm not a lesbian or anything, I guess just bi-curious which scares me because my religion believes that is wrong, but I for real love her so much it's making me not care.

This is getting ridiculously long.. but some more info. I have one strong Christian friend who thought that the girl I like likes girls & said I didn't need to hang out with her. I think if she was anything she'd be bi because she said she's talked to guys.
& now I really want to work as hard as I can to make myself as physically attractive as I can right before I leave for college, & then just gather courage & tell her how I've felt for her & then I'll leave and live 4 hours away from her & maybe I can move on.

So if you've actually read this long thank you so so much. I really just need people to talk to about this. Please give me any advice you have or if you just wanna talk I honestly just want someone to talk to about this so bad because I've been keeping this in for 6 months & its killing me. The reason I think this is obsession is because she is on my mind every second of every day, I do almost everything with her in mind. I literally feel like I need her to live. So, please help me with any advice you have.