Well, I was misdiagnosed with BPD for years and have read a lot about it. A couple of good resources are the book "Stop Walking of Eggshells," for people in a relationship with someone with BPD and the website for TARA, an organization committed to doing research on BPD so that more evidence-based treatments can be developed. Currently one of the best treatments is Dialectical Behavior Therapy ... and, darn it, I can't remember the other one, but I'm sure you'll find it and much more once you start to research this on the Internet. Look for scholarly articles rather than lay people's opinions; they tend to be more reliable, though lay people's articles can help by putting things into plain English once you've got the lay of the land.

Was your boyfriend diagnosed with BPD by a *psychiatrist"? If not, he should strongly consider getting a second opinion and a complete diagnostic interview with a shrink. BPD tends to be a "garbage can" diagnosis applied to clients whose therapists can't figure out how to help them. As the song goes, "it ain't necessarily so."

As for you, if you're trying to cope with someone who is volatile and up-and-down constantly, you might consider therapy too, for yourself. It might help you understand what the "payoff" for you is in trying to cope with such a tumultuous relationship (for instance, maybe it is similar to things you experienced earlier in life and are trying to resolve). Therapy might also strengthen your ability to set limits -- nicely -- and stick to them.

Good luck. Both my spouse and I have PTSD and things are still frequently quite rocky for us, though we are getting better with good treatment including weekly individual and family psychotherapy with a very experienced clinician -- he has 30 years' experience -- whom we're grateful to have found.