First, I am sorry for my bad English skills, I hope you are able to understand it anyway. Please be nice. I am scared of bad comments.. 
Did you also experience something like this? You really love a person but BPD comes in your way.. 
Few months ago I lost a person who was really important to me. We were friends for like 1 year, he always had feelings for me.. After one year we started our unstable relationship and it didn't last longer than 2 months because my BPD was so f*cked up (sorry for my choice of words).
Like, I always try to have a "distance" between me and other people, I am so afraid of everything, but I think you kinda know the way I feel, fair to abandonment and not able to trust anyone, no matter what.
I always wished I could stay together with him and I knew it but sometimes yeah personality switch and baaam everything breaks down. It was always a up and down. I broke up with him but after that I missed him, but he doesn't want a relationship anymore because he don't want to be the reason why I am suffering like this. I want to be with him but I know how toxic it was because of me. Afterwards we decided not to talk anymore but I miss him so much. For like about 3 months I am not able to forget him, I do dream about him and I can't let go.
I don't miss people that easily but damn, this one is so hard. Besides the BPD stuff the feeling of missing someone is so intense and I feel like I am drowning. I messaged him few days ago but he decided not to try it anymore because of the things that happened. He always think that it's his fault but it isn't. It's my bpd a*s.

Sorry for venting but it makes me so idk. I just feel overwhelmed anytime but now this sadness is so painful I can't.