I'm 25 now and I don't know how many relationships I have been in that didn't last longer than 6 months. I've been in really horrible relationships that resulted in me thinking all these break ups were my fault. Please don't make this mistake. You're 20 and still figuring things out and one of the truest things in life is that everything changes and you will continue to change and learn about yourself. But 4 years ago I met the woman I'm still with. I used to always think that whoever I was with, they just had to accept who I was. This is not true and the most toxic thing you can have in a relationship. My SO and I have had to learn to change some things about ourselves and in doing this we have grown such a respect for each other. Let her do her thing, she's obviously still working on figuring who she is or who she may think she is but doesn't know yet. But at the same time, you don't need to stay because she chose you (for the time being). Honestly I do think this one is over and that's not a bad thing. Just no point in staying in this relationship if this is the situation at hand. Same with on the flip side, if your girlfriend had a liking for another woman and not David, I'd advise the same thing. She can't help those feelings and quite honestly, she should find out what those are and/or who she is (gay, bi, straight, etc) and you need to decide if you want to stay to find out if you amount to what she needs/wants. But you're young.. I'm still young! But at 6 months and you're having these issues, it's usually a good sign it probably won't last. Go out and have some fun and you never know what will happen. My SO was in a relationship with a man for 9 years before we fell in love with each other. It just happened. Keep the chin up, I promise you'll meet another beautiful woman.