Guy trouble?? It is long but i'd really need advice :)?

Okay....i have known this guy for a couple of years and i am so attracted to him. He is really good looking and is so funny and smart. We used to text occasionally but since January we have been texting everyday, like every minute of everyday. I don't get to see him that often but when i do we have the best time together, always laughing and joking and staying up all night. Some of the texts are really flirty and he tells me that i have a great body, i dyed my hair and he says it looks so hot and some are texts are really cheeky and a bit rude. The problem is he has a girlfriend, he has been with her eversince i have known him. I feel awful as i really do forget that he does when i'm talking to him but i don't want to it to stop. I am to scared to confront him about it but i feel that maybe he's having his cake and eating it too if you know what i mean. He is always arguing with his girlfriend and they have split up before. I wonder if he is just with her for the physical aspect of a relationship. Any thoughts on whether you think he likes me or why he is doing this?? It is tearing me apart and i don't know what to do. Thanks :) xo