Why does my ex hate me?

we were best friends before we dated. we dated for nine-ish months. broke up. and almost went out again when he said he wanted to stay just friends. i kind of pushed him away and we haven't gotten along since. he's been short with me and in short, treats me like someone he really dislikes or can't stand despite when he says he doesn't and we're "friends". he won't answer my text messages, IMs, or messages if i just want to say hi, but he will if they're for school. i catch him looking at me sometimes, but i can't tell why. i don't understand why he won't talk to me or acknowledge me sometimes. i've gone out of my way for him just to be friends, yet he doesn't return the favor? does he really hate me that much?