Whats my boyfriends problem!?

This doesn't seem right at all. If he was busy with his work then he would of been up front about it instead of making up something about his mom. Also, if he wanted to see you like he said then he would see you. I think you need to have a serious talk with him because this seems weird that he would lie about that... Also it is not healthy for him to assume your cheating when you say be right back. Ask him why he feels like this... A lot of times people who are cheating or doing something along these lines will make up reasons for why the other person is cheating and also lie about why they can't see a person. Not always but sometimes. Just talk with him and see whats going on