<human>: So I was in an extremely brief fwb/fuckbuddy situation with this guy for a few weeks. I've done fwb/fuckbuddy in the past with no issues, but for some reason this guy got under my skin. He ended it a while ago, and 2 weeks later, I'm still thinking about him. 

The weird thing is, he wasn't anything like what you usually want in a boyfriend, or anyone you care about. He admitted that he cheated on every one of his last girlfriends. He also referred to all of his last girlfriends as "crazy" (to be fair, one legitimately had mental problems, but I always think of guys who have a long list of "crazy" exes as a huge warning sign.) He was really, really sweet to me in the beginning, then began to act indifferent. 

I can't say why it bothers me so much. I have a few specific questions here. I catch myself thinking, if I had done x, or y, he would still want to be with me. 

1. Is it stupid to think that I could have changed him somehow? A man who has cheated on every one of his exes will also cheat on his current. I am almost certain of this. 

2. How do you go about getting over a fuckbuddy? I liked him so much that I thought it could be a long term thing.

Can you summarize the given text in a few sentences?
<bot>: I have feelings for someone I shouldn't have feelings for. How do I get over him and was it weird to think I could change him?