Apparently the mood shifts is common in borderline PD... you might want to look into that (not saying you have it of course, it could well be DID) but if you don't have excessive blackouts or memory lapses I wouldn't be overly worried.

It could also just be your personality... but I do know that the "phases" and shifting are supposed to be one of the symptoms. If it's still *you* but you just feel more masculine or more feminine at times, I would say that's probably just normal for you and for some people.