Bipolar ii disorder or bpd...how can i tell the difference?

Bipolar: Bipolar II disorder can be thought of as mood swings from deep depression to a hypomanic (which means not fully manic) state. BPD or borderline personality disorder is characterized by a disturbed sense of self, impulsivity, manipulativeness, thinking of people/things in all good or all bad terms, intense fears of abandonment, sexual/substance use, risky behaviors, and self mutilation.

Either-possibly both: You're raising a difficult question, in part, because both can be present and you may need the help of a professional to sort it out. But, in very general terms, BPD mood swings tend to come on suddenly, last for a period of hours (rather than days/weeks), and often clearly in response to a perceived abandonment. Bipolar patients often say their moods make no sense to them, but can't control them.