<human>: For the past 5 months I have been dating my GF and things have been going great. We (I thought) are in sync and have great chemistry when we hang out almost daily. I love this chick and she says she feels the same way about me..

So here is the problem. About 4 days ago, her ex showed up at her job and supposedly asked her a series of questions (how she was, if he could take her home, who was picking her up, was she seeing anyone). She told him to leave, but he decided to hang outside until she got out at 2am. I picked her up and noticed she was frightened and asked her what was up. She told me what had happened. I asked her why she was so scarred and she said that "this always happens, he shows up and then they end up back together." This made me very upset. They had been broken up about 3 months before I made a move and had no contact since then. This dude is now apparently stalking her outside her house, calling up her home, and his family contacts her as well. 

For the last few days she's been accusing me of not loving her and saying I am a cheater since I talk/joke to girls (classmates). She also gets extremely upset when I talk to  our female friends and they laugh at my jokes. This usually ends with her ruining our night and she later asking why I am upset (which makes me angrier). She also says how I would be happier without her. She is saying that I do not care enough to fight for her and that she was confused about what she felt for me. I've told her that someone that would leave me like that is not worth fighting for. I do not know what to do. Her constant questioning of my feelings for her is starting to make me believe her.

Need any advice.

Can you condense the text into three sentences or less?
<bot>: GF's ex shows up and now she is treating me differently. Hre confusion is starting to make me doubt my feelings for her.