my bad choice

hey so i was at this party last week and this girl from my class who is kinda out of my league comes up to me. we end up in a room alone drinking and stuff gets heated. next thing i know were doing it on the floor, super drunk but also wanted each other badly. felt like cheating cos im with someone but i hadnt talked to them in days so... not sure if its really cheating or just one big mistake. been feeling guilty ever since.