How do I keep myself from being obsessive about a girl I'm seeing...

I've been thinking about an ex the last 8 years. Sometimes it gets better but whenever I'm down (most of the times) I keep thinking of her.

Jesus, this hurts because it's definitely been me. Don't ever do this, for your own sake. I didn't even go that far, but I got close and I still cringe.
Really hoping this is not about to be me.

i feel very powerfully for women too. i hung out and had sex with a girl every day for two months when we were in the same town over summer and then weve been talking for six months after. she doesn't want to be in a relationship with me, and she's "not sure me visiting her is a good idea." she chooses when to text me and will often ghost me for a week at a time. we only skype when i ask, she never initiates. she talks about being in a relationship and that im like a long distance boyfriend to her, but she doesn't want to owe me anything. she says i "need to trust her because thats the only way we could be in a relationship" or that "she wants to see if we could be in a relationship by seeing what happens." she knows i want to date her and uses that carrot on a stick to influence my behavior. i know for a fact she doesn't hook up with anybody else because im in her life, but she does say she wants to keep her options open.

and im such a dumbass that ive been chasing her for six months. every time she gives me a little hope like she agrees for me to visit her, ill treat her like my girlfriend and then she cancels on me. and i just go back and forth in like a cycle because i convinced myself i wanted to spend the rest of my life with this girl when we graduate college. but im just a dumbass. im really aloof and i dont care about girls usually, and i always treat her pretty normally when she is being a bitch. but like, when she tells me something like she needs me in her life or that she doesn't want to lose me or that she needs me to trust her, i immediately lose my head and give her affection and then it falls out from under me. every time. and im so scared to think about her fucking somebody else that i just act like a dumbass every time.

Sounds like me user

We can break out of these shitty cycles

Best thing to do is talk to other girls you find attractive.
You can’t know how many other guys she’s talking to, but if she was that into you she’d be checking your messages as much as you check for hers

its just so scary thinking about letting go for some reason. i feel sexual desire towards other women, and its not like im awkward when it comes to casual sex. its just as soon as this element gets introduced i feel like if this person that i care about now has sex with another person then i just feel terrible. it makes me snap and just break down. i dont want to let go because then i know she'll find someone else to manipulate the same way but she'll likely be fucking them all the time.

Need to respect yourself more mate, and not give someone else that much control over your emotions whether they realize it or not

yes sir. we've planned to skype this week and im basically going to tell her that
- shes ghosted me this past week and is never too busy to text me more often, shes just choosing not to
- she never initiates a skype call
- she doesnt want to cooperate towards me seeing her, she doesn't think its a good idea in theory

then i do not want her in my life because what is the value of a long distance romantic connection with literally nothing left

and then she'll try to pull me back in at some point and ill tell her that we'll either be in a real relationship where she makes good on her word and wants to see me or its nothing. and then she'll lie to me and say she wants to do that, and then ill still tell her to leave me alone until i see any proof that she's not just using me to be a texting buddy and give her attention. id maybe even be fine with a casual friends with benefits thing, but she just takes it to a place of manipulation every time. its like no matter what we cant be on the same level in a cooperative way. its very irritating

I was diagnosed BPD years ago and I realized it had a lot to do with me acting like this. Takes some practice but you can unlearn this behavior. You just gotta keep mentally occupied and do your best not to obsess.

Sound like me minus the fuck part.
But I know I would be like that.
Fuck this shit

Try to remember the last time your compulsive obsessions drove a girl to dumping you. Try to remember the slow-burning heartache that seemed to last longer than it should have.

Then gain some fucking composure as a man and try to keep it

Find a new girl to pour your heart and soul into

Do you imagine her performing sexual acts while you are cry-fapping?

Either confess to her or fuck off.
I've been there OP.
It's not healthy and can fuck you up if you keep hanging around people you're strongly attracted to.