I (M18) cheated on my girlfriend (F21) at a concert she brought me to

This happened a few months ago in the spring. I went to a concert with my girlfriend and her friend from her college. She’s a couple years older than me so I was just visiting her at college (I don’t start until later this year) and had never met her friends before. It was at a large venue and we had GA tickets. In GA we ended up talking with a lot of the people around us and we were all drinking and having a good time. There was a girl there with her 2 friends all from my girlfriend’s school who was chatting with us but my girlfriend didn’t really know her. She and I talked a bit about the band we were seeing and some other upcoming concerts we were attending. The band started and she got really drunk really quickly. As the concert progressed she was starting to push her ass up against me while i was standing next to my girlfriend. I tried to keep my distance so my girlfriend would not get suspicious but each time I moved away she got closer. Finally my girlfriend went with a friend of ours to get another drink and go to the bathroom. This girl took this as her opportuinity to grab my hand and let it wonder. I started feeling up under her shirt and pinching her nipples. she reached behind her and started grabbing my dick through my pants. I moved my hand down and started fingering her over her pants. she was grinding up against me hard at this point and so I stuck my hand down her pants and started fingering her roughly. she was ready for me to fuck her right then and there and if I wasn't with my girlfriend I probably would have. I knew I had limited time until my girlfriend got back so I took my hand out of her pants, licked my finger with her pussy juice on it, and then stuck it down her pants and straight into her asshole. she gasped and told me to fuck her. I told her to stop that my girlfriend was coming back. my girlfriend walked back over maybe 20 seconds later and was unsuspecting. The girl did try to keep rubbing against me after and I kept my hands in the air and told my girlfriend she was just drunk and to not worry about it. We left the concert and I kept pretending to rub my nose so i could keep smelling her on me as we walked out of the stadium. I never saw her again after that lol but I do still think about her