Is it okay to text a guy who has a girlfriend?

This guy and I took a cl together, but we also have mutual friends. We talk at school, and about a month ago or so he started calling, texting, and flirting with me. I didn't really like him back or flirt all that much, but recently my feelings for him have changed. We don't talk on the phone because I find it awkward and I just don't like doing it. One night we were texting and flirting, but then he dropped the biggest bombshell on me! He has a girlfriend. I don't know her because she is either at a different college, or she's still in high school. I don't know, I haven't really inquired about her. Anyways, I really like him now and its hard to just stop liking him. I really enjoy texting him, but I feel kind of guilty. Not too much though. I would never do anything that would cause him to physically cheat on his girlfriend. What should I do? Thanks for any and all answers!! :)