Should I say something???

Okay, so my boyfriend and I have been dating for almost 2 years now. We met through mutual friends at a party. Before I met him though, I was already friends with his friends for a good amount of time. One of these guys is his best friend from high school and still one of his best friends to this day.

While my current boyfriend and I were still just "talking", his friend and I had some stuff happen. He came on to me one night down by a creek and it was everything BUT sex (we were both a little drunk) but I stopped it and told him we should go since we both had a friends party to go to. Then about 2 months before my boyfriend and I made it official we did the dirty :/ I had to stop over to get a bottle of liquor that I left at his place since we all had a get together the weekend prior. It wasn't that I wanted it to happen (because I already felt horrible about myself from the creek incident) but it happened very quick and I still remember going home and balling my eyes out because I couldnt believe I just did that with a guy I likes best friends.

I told my boyfriend about the creek incident and he said he isn't that upset because it was before we were dating and evem official. But should I tell him about the other incident too?

This same friend slept with one of my boyfriemds girlfriends so I feel like he will hate me if I tell him tha happened. I want to be honest with him but I also don't want it to cause a fight with us.

If it was before we were dating should I even bother? I am not the type of girl to sleep with any guy so I don't know why this happened or why I gave in so easy to him. Should I just keep it to myself since his best friend now has a girlfriend? I don't want to ruin their friendship that has been going strong for 12+ years after high school

This has been eating me away and I need some advice....please no rude comments. Just need some help in an awkward situation.