What's Happening?

I don't know if this should be in this forum but I guess hormones could be contributing to my problem.

So, I'm 17, thankfully healthy, except for my PCOS,which I take birth control for. But ever since March of this year, I can't stop thinking about suicide after I heard one of my schoolmates had committed it themselves. I didn't know him except for his name and his face, but I'm guessing hearing about him kind of traumatized me. Two years ago, I had OCD about my sexual orientation and I fell into what I think was depression a few months after I self-diagnosed it. I also thought about suicide then but I was terrified about actually carrying it out. I couldn't hold a knife or look at pills because I was so scared that I wanted to actually kill myself.

Now, after that ordeal was over and after spring break when I heard about my schoolmate, I've been questioning life and why we should be here. It leading me to suicidal thinking but I think I don't want to do it, I just want to be happy again, like I was before my OCD. I've looked up depression but it doesn't fit me except for the suicidal thinking. Don't get me wrong, I don't have a plan or anything, I'm just confused as to why I'm having these thoughts. I just want them to go away, or at least find a good answer to why I should be alive. I'm eating well (little bit of junk food here and there), I stay at home all day because it's summer and all my friends are on vacation but I do have a couple of hobbies to keep me content. I haven't been able to sleep well this last week because I'm scared of having nightmares, but I can function when I'm awake. I have plans for the future and can spend hours daydreaming about getting married, having kids, and going to work (yes, you read that right).

Could it be that my birth control (Marvelon 28) is affecting my serotonin? Or is it because I'm a teenage?

How can I get over this stupid, obsessive questioning about life, because I'm sick of the non-stop thoughts about how life isn't fair or how I'm truly insignificant in the grand scheme of things. I just want to be confident in my will to live again. This happens anywhere and at any time so I can't track it and it's making my life miserable and unbearable. When I forget about it for more than fifteen minutes, it shows up for no reason and I fall back into the loop of questioning life and reasons to live. Also, if I'm not questioning my reason to live, I'm always on edge because I'm afraid my mom will commit suicide (which I know she won't because she's heavily religious and a tough cookie). It's just the whole idea of killing oneself to escape things that got me because now, whenever I have a problem, my brain just gives me the expected thought and I end up going into my very own mini existential crisis instead of trying to solve the problem.

FFS, both of my parents are engineers, is it that hard to activate the problem-solving gene?

By the way, my thinking doesn't cause me any anxiety, it just sounds so annoying in my head, I feel like the only way to get rid of it is to commit suicide, which triggers the questioning, like, why did I think that? Do I want to do it? How would it feel? Will I be finally happy?

I'm sure someone else has gone through this so I just want to hear how people have gotten over it so I can finally be free from this hell.