Am I being selfish if I pursue it?

WTF is wrong with me?! I really have some serious feelings for a coworker. He has a girlfriend but I don’t know how serious they are. Im not going to do anything with him while he has this girl but I’m getting some vibes off him. We were super drunk and kissed but I said that I wouldn’t have sex with him because he has a girlfriend. Should I just hold onto these feelings or what? I’m so stuck between being selfish and sticking to my morals. You know how you just know that he is the one? I’m getting those feelings. Please help xx