Am i a bad girlfriend? How do i overcome this?

Ok so iam in a perfect relationship we are very happy, weve been together for 3 years. Hes a really lovely person but something happened.. so on his biryhday o was feeling a bit distant from my bf and started thinking about his friend.. he showed me more attention.. i started to think that what if i like him? What would happen if he kissed me and silly stufflike that.. then everyone who was at the birthday party went to my bf room and my bf had too much to drink so he fell asleep on the couch and the rest of us were on the bed still drinking and i let my bf friend put his arm around me and we fell asleep like that... i liked it.. iliked the attention... now its beena month after, my bf said i did nothing wrong but i feel diferently because of my thoughts... ifeel terrible even though everyone said that i didnt do anything wrong and its normal to have those thoights sometimes but i still feel guilty... what should i do.. i love my bf very much hes amazing but i feel like i did sonething that he would never do to me and feel horrible about it.. i cant go about my day without having a breakdown about it... whats should i do? Did i really do nothing wrong..?