I really need advice

So this guy and I have had a flirting thing for a while but we would never act on it and we were both in relationships. I broke up with my boyfriend and the first chance we had we were making out all night in the club and then he came back to mine and we hooked up. We were both really happy I mean we both have feelings for each other but he still hasn’t broken up with his girlfriend. He says he is going to do it after her birthday next week but I’m feeling really guilty. I am supposed to hang out with both of them (and the rest of our group) on the weekend and I don’t know how to react. I feel bad for her and feel really guilty and what if he doesn’t even break up with her?

What do I do!