Awkward Situation

Hey guys! So this past weekend, I was hanging out with 2 close friends, 1 guy and 1 girl, watching movies. The girl had to leave early because of weather. The boy stayed we made it through 3 movies, took a walk, had some adventures, and ended up staying up until 5:45 am. That night the boy and I made a pact to get married to each other at 28 if we are single. The next day the boy came over again and we watched another movie. We also went outside again for fun. When we came back in we layed next to each other on the couch and even spooned (with me as the big spoon) for a while. We planned our whole life as if we were getting married at 28. We rated ourselves and each other. We also played truth or dare and the truths got pretty sexual and personal. There were even a couple tickle fights. We ended up pulling an all nighter because we were just feeding off each other’s energy. He had multiple opportunities to leave throughout the night but stayed until we left for class in the morning. The difficult part is the fact that he has a girlfriend.

What should I do? I know we obviously need to talk about what happened. I really don’t want to ruin our friendship. Help ya girl out

Update: we talked about it and I told him that he needs to tell his girlfriend about what happened because he would want to know about if she did the same thing. He kept using the excuse “but we didn’t DO anything” but I don’t know what else to tell him. I really didn’t mean to get myself into this situation. I’m not trying to steal him from his girlfriend we are just generally good friends and this just happened while we were hanging out. There are many smaller details that I left out, I just don’t know what to say to him.