Do some of you GUYS know why he is acting like this ... mature answers only?

my bf of 2 yrs we broke up, we lived together for half a year then broke up and decided to be friends. Now other guys are interested in me and I've been asked out but i still have feelings for him so I said no. when i tell him this because he was asking me all kinds of questions trying to figure out who asked me out but i refused to say then he got mad and said "see this is why we would always fight, you don't answer my questions fully." I said no I wasn't gonna tell him. he asked if it was one of his friends because when he saw me today he saw a lot of guys checking me out. I asked "why do you care?!" he said he doesn't but then he started calling me names like crazy and stuff like he was mad at me or something so I said "fine, whatever, I guess I'll just say yes next time!" and walked away. He thinks I do things to be near him and i don't i go to school and so does he I am not his follower! it gets me so mad! he was the one who subtly was telling me to take the same cl as him but i need this cl and I don't see his name on the cl like it's all his what a conceited guy! why is he acting like this we agreed to be friends with no hard feelings! i think he used to love me a lot and I did too, we were at our final straw in our relationship so I was the one to say we should be friends! but he'll call me nicknames still like when we were dating like sweetie and stuff ughh i don't get him!