I have a dual diagnosis or bipolar and borderline, and I agree that what you have described are my borderline struggles, not my bipolar at all...

The chronic emptiness and boredom, the chameleoning between different types of friends, (root being identity disturbance or more accurately a lack of a solid identity) the erratic moods shifts based on how others affect me, the pulling people off of the pedestals I put them on when I percieve that they've wronged me, the irresponsibility when nobody was available to reign me in...

I'm not a dr though, so I'm not diagnosing you. I'm just a patient with sometimes way too much insight into my crazy for my own good.