what do you think.

so I've been best friends with a guy since middle school. he's been like a brother to me but I also have feelings for him too if I'm being honest. he knows thus and it's fine, nothing changed in our relationship, still best friends. he has a gf and me and her are pretty good friends. thing is they are in a long distance relationship and he just told me he doesn't feel the same toward her and he's thinking of breaking up with her. Then about a week later he asked me to go to prom with him and I said no because he had a gf and I didn't want to be rude. Then about a month after that he asked me to move in with him, he lives alone. he is my best friend but I'm getting scared because idk how he feels about me. and if he is getting feelings for me I'm gonna feel bad for his gf because me and her are friends also. what should I do? please comment.