BPD or not?

I'd like to start by saying that, no. I am not trying to self diagnose myself. I don't think that mental disorders are "cool". I just need help. Recently my life has been great. I have decent grades, my group of friends and even a girlfriend. The thing here is, I don't know who I am anymore. One moment I'm a stereotypical shy girl. The next thing you know I'm the "funny" one. My personality is everywhere. Hell sometimes I even talk to strangers with a British accent (I'm not even from Britain). I feel like I've lost sense of things and especially myself. I don't know who I am as a person and how I feel about the people in my life. I've mentioned the fact that I have a girlfriend before and I love her. But somewhere in my mind when she doesn't talk to me (I know she's shy and is sometimes busy) I feel like she hates me and I'm not worth her time. A few hours later I'm in love with her just as I was when we started dating. What sucks is that I know I act like this and I literally can't help it. I did some research and my actions may be symptoms of BPD. Once again I don't want to diagnose myself. But I can't really speak to a professional which is why I want some honest opinions from people who are diagnosed. If I really don't have BPD, I don't know what's wrong with me. But thanks for hearing me out.