i cheated on my partner

so last night i went to this club downtown and met this girl, lila. she was so into me from the start, like she could tell i was feeling down about school stuff. we ended up at her place for a bit and things just kinda happened...we were both pretty wasted but it felt intense, electric really. afterwards i tried to brush off the guilt cuz it was one night and id break up with my partner anyway soon right? but now thinking about how he trusts me and loves me unconditionally makes me wanna puke. gonna have to come clean eventually but im so scared of losing him. maybe this will be good, a reason to end things before i mess up even more.