what is up with him?

ok so me and this guy broke up like a few months ago and he told me to leave him alone so I have been. but like a week ago I saw him at his work and he was really nice to me and stuff and like said that he missed me and stuff…then the day after he texted me and wanted to mess around and I said I didn’t know if I wanted to because of what happened so he got mad so then school just started back like 3 days ago and in class we can choose where we want to sit. and so I sat in the middle of the room…well there were like at least 10 open seats opened after he got into the class and he sat by me and the hole time he was staring at me. then to day I ran into him at the mall and he called me ugly and fat. what is up with him…