Why are guys jealous of girls?

theres this guy and he's VERY jealous of me for some reason and i cant understand WHY... i mean, he's a GUY. what would a guy have to be jealous of a girl for, and he has a bitchy attitude(female doggy if the word is blocked out) no he's not gay, but... WHY. im a girl for goodness sake, you can be jelous because im pretty or have things you dont have, because guys have different taste and style in stuff... He's so mean and acts like a girl alittle with his attitude problem. he feels the need to make comments about my body(which he's fat, and i KNOW I have nice curves) and he gets upset when i wear heels. I like to dress nice. I wore skinny jeans with high black heels today and a white button down collared shirt that has pockets(with little gold buckles on them) and gold button... guys look at me and like the way i dress, its not slutty, but very sexy in a classy way.. i dont know, whats his problem??? i was standing outside today and he yelled something at me. when i went to him, and asked what was said he said "if your ears were open the first time, you would have heard me" bobby his head around the way a black girl would when she's being a smart allec.