i cheated on my boyfriend

so i have this bf we've been dating casually for about 4 months now. nothing super exclusive but he calls me his and stuff. so anyway last week at a party, this girl comes up to me who is kinda cute and flirty. she's like hey can i get your number? then the next day she sends me a message asking if i want to hook up bc we both know our bf’s aren't around this weekend. at first i was all no way but honestly i really wanted too, and my bf hasn't been feeling me much lately so... yeah one thing led to another and we did it. we used protection ofc but still... its not like i love her or anything i just kinda wanted out for a night, you know? now i'm thinking about how i feel about this and what my next move should be. honestly tho, if the opp presents itself again, i'd probably do it again. im sorry to him but at the same time i dont feel super bad either. its weird.