hella confused

I honestly don't understand guys at all. So the guy I like I've liked since like July when school first started and we have been great friends since then like we have 3 classes together and we always talk in those classes and last week he seemed like he liked me as WAY more then a friend then this week it was back to normal and then yesterday in class he moved to sit by me and he was talking to me non stop and we were having such a good time laughing so hard and even my friend could see he was trying hard and that we were flirting and I could tell he was really into and genuinely happy to be hanging out with me then today he's acting all weird like he pretty much only talked to me like  once in my first class and like a couple other times the rest of the day like I don't understand how he can seem so into me one day then not the next? What do you girls think? I really like him and I really want things to happen with him but i honestly don't know if he just sees me as a friend or not.