I've experienced it, and it's really not a good thing to let fester over the years. After I (finally) found effective treatment, I realized that it wasn't that I liked it, it was that I had no idea there was any other way for me to be. It's something I can backslide into, but it's not a necessary part of my personality. In retrospect, so much of my time living in Chicago while I was in grad school was lost to this holding me back, musically, socially, and professionally.
Bpd could be it, but this is also common to Bipolar II. Bipolar II's have fewer, less intense manic episodes, but cycle more frequently and tend to reside more on the depressive end of the spectrum. And as Bipolar II's age, the "up" parts of the cycle feature less happiness and confidence and more agitation and anxiety.
Be patient with your treatment, and if it's working, you'll be able to act more in tune with your true feelings.