Hey there-- I just re-started therapy and haven't been officially diagnosed yet but I suspect mine is a toss-up between the two you mentioned: BPD and Bipolar II rapid cycling, because my moods can change on a dime. I relate to both disorders too, and could be fit into both, and I do not self-harm. I do have suicidal tendencies though, which is also an aspect of BPD and the downs of bipolar. You don't have to be a cutter or anything like that to have BPD, even though that type of self-harm is common. Other illnesses can occur with BPD too, like anxiety disorders, obsessive compulsive disorder, eating disorders-- for instance I was diagnosed six years ago with anorexia nervosa, which is common with BPD. Also, if I'm remembering correctly Bipolar II doesn't include full mania, but BPD causes compulsions towards two or more self-destructive acts during your "up" times, which maybe wouldn't be something you would experience with Bipolar II, where it's more just feeling really good and overly energetic? Also Borderline means intense irritability, a tendency to be easily hurt and angered, loving someone to death than hating them two seconds later, which causes a lot of relationship disturbances, a feeling of emptiness that makes you do "crazy" things (promiscuity, spur-of-the-moment trip, shopping spree when you can't afford it, etc.)-- these are all parts of BPD that seem different from the ups and downs of Biplor II . I guess that for me, what mainly sets the two apart is how people with Borderline continually sabotage their relationships even while losing those relationships is the worst thing they can think of. If that is something that has happened to you a lot in the past then I would talk to your doctor about the possibility of the Borderline diagnosis. In fact, talk to her/him no matter what, because I am far from an expert-- I've just been reading up a lot lately on Borderline since I think that's what I will be diagnosed as a few more sessions in.

Good luck!