pls give some relationship advice

So like this is my first relationship at 23y.o, so my partner before we confirmed our feelings for each other and made it official, we went to a pool party two days before and got super drunk and high. The issue is I have a a bad habit of kissing people on the cheek whether they are nice or not, so this guy let's call him L, he is a cheater and flirts with a whole lot of people he was there at the party (he was lowkey interested in me but not really) and I have bitched about him with my partner before, but idk what happened few days ago my partner heard that I kissed the L guy, I have 0 memory of doing that like none at all and one of my other guy friend also said that L has a video of me kissing L on the cheek apparantly (i personally have not seen the video).
My partner is very sad to hear that I kissed L , they said we shared so many romantic moments together and did so much and i talked about my fear of being cheated on and stuff. I honestly don't know how to react to this, is this cheating idk i really do like my partner and we've been dating for almost a month but rn it's long distance.
Please suggest me something so that I can come to conclusion and talk about this clearly cuz i really don't know how to react to this situation. I'm so tired of feeling guilty when I myself don't clearly know what I have done when I was drunk even my partner doesn't remember most of that night becuz we were so damn drunk.
Any tips will be appreciated.
Sorry for the long ass paragraph but I just had to add all the details just in case.
Thank you and i really appreciate yall for reading this