Girlfriend is very selfish?

Well, first of all, you can't blame anyone but her for the way she is acting. Not her past, etc...she is responsible for the decisions she makes and how she treats people. And secondly, long-distance relationships are really hard, and for things to work out you can't be feeling uncared for and like all you ever do is give give give, and she gives nothing in return. She is sucking the life out of you. I would give some thought as to whether or not you should stay with her; there are other girls out there who would be far less difficult and would appreciate and care about you just as much as you care about her. Good luck. :)