I don’t know what to do

So I went to this party on Saturday and ended up sleeping on a sofa bed with this guy... let’s call him Kai... so I’ve only met Kai a few times and didn’t really know him but he’s friends with my best friend... anyways we shared this sofa bed and were up almost all night talking cos we couldn’t sleep... we ended up cuddling and he kissed me but the next morning I found out he has a girlfriend.... I’m really attracted to Kai and I was honest and told him and he said he was attracted to me but he had his girlfriend and now I literally can’t stop thinking about Saturday night like it’s been the best night in ages but he’s got this girlfriend who I’ve never met so Idk what their relationship is like.... please help 😔