Talk some sense into me

I left my uBPD ex about a month ago. I'm female, he's male, if that means anything. We've been in loose contact — initially it was him freaking out on me for leaving him, then after he apologized and started leaving me alone, I drunk-texted him that I missed him (my bad...), then he announced he was moving back into our apartment and that I could move out if I didn't want to be with him. I did move out, which I don't think he was expecting. The next day, he asked me to come back, and I said I'm sorry but I just don't think it will work out. I've been staying with friends, house sitting for a family I know that's on vacation, and planning to rent a room starting next month. But then, yesterday, he texts me saying that he goes to bed and wakes up every day crying, that he would do anything to fix what's been broken between us. He asked me if I'm happier now, I said in some ways yes, in some ways no, but mostly I just feel lighter.

Today, I happened to be in the area of our apartment, and decided to stop by to see my cat and drop off litter and other cat supplies, since my cat is still living there and my ex has been taking care of him. The ex wasn't home, but I spent about an hour and a half there, just marinating in memories and emotions. I lied on our bed and cried and thought about everything I loved about him. I noticed that he's been keeping the place clean and that he even got out his easel and art supplies. There was a part of me that just wanted to stay there, wait for him to come home from work and have amazing make-up sex and try to be together again in this comfy home that we built together. There is another part of me that knows it will never work out. And then there is this other part of me that thinks, maybe he doesn't have BPD after all. I literally just concluded that on my own after reading articles about it, but I've never hinted at it to him, or heard anyone else say he was BPD. I don't even think he knows what BPD is. And, what if I'm wrong? I'm no psychologist. He obviously has some personal issues to work through, but who am I to diagnose someone with a personality disorder?

Ugh. I'm hurting. I miss him, and I still love him. Talk some sense into me.

UPDATE: Just wanted to thank everyone who responded. I really needed this.