Replying to Girls you really like fucking with your mind

So I met this girl two weeks ago and she was really in to me so we hooked up then. We spoke the weekend after it happened and we were totally cool. Then i get the impression that she has lost interest because she stopped calling but I see her and were back on again. Then last night i was at her house and was so cold towards me. Normally i would not care but i really like her and the whole situation is pissing me off. It is so complicated and iv only known her for 2 weeks. Im going crazy. Maybe the girls on here could tell me what the fuck is going on...please!
Dont go to England...E V E R