The guy i have been dating has a girlfriend?

I feel so stupid! This guy who I met at each others work asked me out and we have gone on 2 dates he's 4 years older then me so I need to sneak out to see him. We went to his house and he closed his facebook but I saw his last name and I looked up later. Well he is in a relationship with some girl! I feel so bad! And so stupid! Should I ignore his texts and the next time we run into eachother ill tell him what I saw?