I best friend and I were drunk and had sex?!!?!

My friend and I were partying this last weekend and we both got drunk and we went down on eachother the best day we just woke up super hung over and didn't say anything about got but now I fagly remember all the stuff we did I have been working do I havnt seen her but we text I'm with a guy that I've been with for 5 years I'm scared to tell him I have no idea what to do!!?