Why do i push him away?

Well, i have been dating my boyfriend for.. um, well say more than 2 years now and he plays this online game every time he gets a chance. He will stay up late to play that game and even come to school tired from it. Well, I cant help to feel a twinge of jealousy towards it. See, every time he plays and i try talking to him all he says is " okay. ok. k, or lol." its quite annoying actually. But its like he would rather spend his time playing the game then be with me.. well not like, It IS that he would rather play his game... and who would blame him? The problem is my reaction. I always bring it up and start being all moody about it and complain about that game. But the thing is he gets really mad at me. but i don't understand why it is that hes mad. I don't think its that i bring it up either. I think he finds my nagging amusing. My question is, how am i suppose to stop? Just only talk to him at school and let him have the other time with the game?