Would love to help someone solve their mind related issues.

this is going to be my first post, i'm not really sure where to start this post so i'm going to jump right in, i have a been wondering lately whether i may suffer from borderline personality disorder, i have had this feeling for a long time that i am not quite right, i have this emptiness inside me, it feels like i am a camera stuck on live feed but no ones watching, i often feel like this regardless of whether i am content or unhappy.

onto how i feel, sometimes i lie awake at night reliving the past day, i feel ups, downs, and sometimes a cold icy rage. i have little control over my thoughts and feelings at these times, or anytime really. i can maintain at times, but only for seconds before i'm lost again. during the day when faced with interactions with people at work etc. i wear a mask that's all smile and charm, at times it feels more real than others. when like this i have little room for empathy or genuine care and affection, because one chink in my armour it could all come crumbling down. regardless of this, time, tiredness, stress and everyday interactions slowly erode it away. the harder i try to keep it on the worse the emotional comedown is. at home i can hide away in a book or hobby, at work i will feel like a zombie, just going through the motions, lost.

i have always known that i have a very adaptable personality, it became more clear with a friend recently pointed out to me, that i completely change, interaction to interaction, almost instantly, depending who is around, effectively becoming a different person. i think i choose the path of least resistance, the easiest and the safest. at times it feels like i am just mirror, lost in someone elses reflection. my lack of self has made me easy to be manipulated and used for the benefit of others at times sadly.

the people i allow myself to care about seem to effect me the most, i don't wear a mask with them, even if i wanted to i can't , this can result in myself becoming this mirror colored thing, for the most part i don't mind because we are happy, and i am more comfortable asserting myself, or the self i want to be,

i think this has been a pretty long post, i will leave it here. if there are any questions i will be happy to answer them. thankyou

I just don't understand my "family". I leave my purse and wallet out on the table and they come and go through it. They just pick my wallet up and flip through my check book. And when I said something my grandmother got mad. She just got mad and smarted me off, then walked away. It's like this all the time, it's like I'm supposed to let them run over me and do or say whatever they want about me or my stuff, and if I say anything I'm a bitch or I don't know what I'm talking about. Honestly it makes me sick just to be here. Sometimes I just feel like I can't take it anymore, like my time is over and I should just commit suicide.

Ok, so I'm pretty sure there is something wrong with me. I have had this feeling toward my stepmother since I could remember. Like a desire. I know it's wrong, it's not right because she is married to my father and she is my stepmother. My father cheated on her and I just wanted to tell her so bad how I felt about her, and how much she deserved better but they got back together. My father married her without telling her he had a vasectomy. And all these years later she really wants a kid, I wish I could help her have a kid...
I am 21 years old, and I moved back into their house about a year ago because my roommate moved out of state and left the bills all on me. I go into their room sometimes when they go to work and I smell her freshly worn panties, and masturbate to them. I found a box of her toys(dildos) and I masturbated to them and licked them. I also found their sex tape and watched it so I could see what she looks like naked. Sometimes when my dad leaves to go to work, I hear her getting into the shower and I fantasize going in there and joining her, or going into the room and waiting on her to get out.
I have control enough to never do anything to crazy, but what should I do? Should I just get help, or tell her what I have done/ how I feel, or nothing? Please don't comment how sick I am, and how I need to find god.. I know I am sick, I just can't control myself sometimes.

I self harmed for two years. I began starting a new coping skill that has been really effective; eating. Although, I'm worried because I had a slight eating disorder before, eating might draw me back in it agaian.