BPD? (Quiet BPD perhaps?)

I know this is not used to diagnose, but I worry about my boyfriend. He is in his mid 20s, stays isolated, history of drug abuse (in NA now), attempted suicide in early teens, and tells me he must keep guard up to prevent getting hurt as his former partners were supposedly very hurtful. My main complaint here is the 1-2 day long silent treatments. We don't argue, but he has this hot/cold push/pull thing. I have spoken up assertively about the silences, and he claims he is like this with everyone or gets depressed and must retreat for a bit. He insists it is not personal, but it is taking a toll on me. Any of you guys relate?

I dated a guy last year for about a month, then I ended it due to his push/pull tactics. Why I thought it was a smart idea last month to reconnect is beyond me! (Well I'm tired of being single)
He now lives at home, but seems not to talk to most people aside from his family. He used drugs and attempted suicide (sober) in his teens, but takes an antidepressant and goes to NA now. We don't fight, but he will ignore my texts/not initiate a call or text for a day or two even when he doesn't claim to be busy during that particular week. I have politely asked what's up, and he says he "isn't great at staying in touch with people", or he blames it on the depression and general avoidance. I have never excessively contacted him, not do I think I expect too much. Even he agrees. In reference to issues like taking this relationship to a more serious level, he says he cares alot about me, but has his guard up after all of his ex gf's hurt him. All of the above happened last year....after we broke up then, we were NC for a year, he welcomed me with WARM, open arms initially, and now we are back to square one. I don't think he is a Narcissist, but something about this doesn't seem right.

Well just from my personal experiences men can be BPD too, it's a painful disorder for those who have it, but a question -

What was the appeal when you met him? The question is about turning it around from him to what drew you in? If you don't understand your own motives, how can you help him if he has BPD?