A little background: I’m a female with BPD, 23, living with my boyfriend, 22. We’ve been together for over a year. 

Everytime we fight, he used to shut down and completely ignore me. I’ve learned to calm myself and attempt to explain myself and my feelings when we fight (which I’m very proud of, I never used to be able to do that). But he would tell me he can’t take it anymore or that he doesn’t care about us anymore, even when there’s no shouting, just whenever there’s a disagreement and we’re not happy go lucky. So the routine would be me crying to myself  until I fall asleep and the next day he would act like nothing happened. 
This fight ensued because since the school year is starting for him,  (I am now working full time), I’ve started feeling insecure since it’s a change of schedule, potential opportunities for meeting new people, we’ll be spending less time together, etc. 
Yesterday, he says he wants to start going to the gym again, and it brought up a lot of insecurities in me. I just want to say, I understand it’s illogical. But when I used to gym at school, I see how guys check me out constantly, and it just makes me so uncomfortable. Especially being a campus gym, everyone is our age and to be honest, when I used to go, I always made sure I looked presentable because I know we all check each other out. 
On top of that, he bought a new pair of $200 jeans and a $800 jacket in the past few weeks, and it’s making me feel like he’s trying to look extra good since he’ll be at school. (It’s a small campus, with only several buildings, pretty much like a high school) Of course, this kicks up all sorts of insecurities and I start sulking and I sit there silently, holding back tears. (It makes me even more upset that this even bothers me) 
He launches into a defensive mode and continuously says “What the fuck? It’s the fucking gym.” This makes me feel even worse because I know it’s irrational, and I’m trying. The old me (with my ex) would have gone bat-shit crazy, outright saying “No you can’t go” and just full-on borderline rage, spewing ultimatums left right and centre. I’ve come a long way, but it feels like it’s still not enough. I’m trying so hard and it hurts so much. 
With my dbt skills and years of therapy, I tell him calmly why I think I feel what I feel. I tell him this is just my insecurities and maybe we can come up with a solution, like going to the gym together first? And when I slowly see that there’s nothing to worry about, he can go with his friend. (It also doesn’t help that he told me when him and one of his friends used to gym, the friend would keep checking girls out and telling him to look at that ass, etc.) I tell him we’re a team, and I don’t want to be that girlfriend who controls him. And it isn’t coming from a controlling state of mind, I’m just very insecure and I want us to come up with something that makes us both feel comfortable.
He just kept saying, “What the fuck. It’s the gym. I can’t have my own life? I don’t care, I’m going.” He knows I have BPD but it seems like he just doesn’t want to work with me through this. I just want him to ask me nicely why I’m feeling this way, and tell me it’s okay, let’s work on this and come up with a solution so we’re both happy. I just want him to tell me he loves me and although he can’t not go just because of me, he will try his best to make me comfortable. To make it worse, when I was pacing around the apartment, crying, he was smirking and I asked why he can laugh at me and he said, "It's so amusing that you can be this upset over the gym." I was shaking and crying because that's just so fucked up. I was obviously so tormented. 

I’m trying so hard. I really am. I’m going to go back to my parent’s house for a couple of days, which is hard because I work 5 minutes away from where I live now, and my parents live 2 hours away. I think this relationship is doomed, I’m trying so hard to be dialectical and he just shuts me down and I can’t force him to talk things out with me. 