I feel guilty

I have been broke up with my ex for about 3 months now. I have been crying so hard the past 3 months because I'm so in love with him and I hate how it ended. I tried getting him back but he avoided me and barely talked to me. And i couldnt take it anymore and it was hurting so bad I wanted anyway to move on. I thought doing it with someone would make it all go away so i got drunk and did it with someone. But i woke up feeling disgusted at myself and with the person. Ive never just hooked up with anybody like that. And the next day my ex finally talked to me again about there being a possibility of getting back together. And im so confused, because if we do get back. Would it be something i should tell him. I feel guilty and i feel like i cheated even tho we werent together. I just thought he was completely done with me barely any contact .