Question for guys: whats wrong with him?

It is really difficult to just have a fwb. Most of the time one of the friends gets their feelings hurt. From experience, it sounds like this guy likes you. He is jealous you are talking to his friends and now he is being cold. He knows he likes you and is trying to keep from showing his feelings or having them hurt anymore. It is not your fault, he just had a change of heart clearly. I would talk to him about it and then maybe give him some space. Even though it sucks I also wouldnt continue to sleep with him until the both of you can talk it out.