cheating while drunk

okay. currently I am having a "thing" with a guy, not so much of a relationship, but people know that we are together. I do not quite feel a connection with him and I feel as if I'm holding on to nothing. he cares about me a lot and I care about him too, but I feel as if we're not on the same level. 
at a party last night there was a guy who I really liked months ago (he also liked me) that tried to kiss me the moment I  hugged him and greeted him ( he was extremely intoxicated) I too became extremely intoxicated and eventually ended up kissing him later that night. even though hehappened in the past the feelings are still strong. 
what should I do...?