My boyfriend's best friend slept with me
One night, me and my boyfriend had his friend round and we went out for drinks. We were all pretty drunk and when we got back home, we had more drinks... then my boyfriend and his best friend had an argument about something (I can't remember how it started) so my boyfriend went upstairs to bed.
His friend was saying awful things about him and saying that mine and his relationship was toxic (I can expand on this if you need me to). His friend was going through a depressive time and so was I and it felt like no one else wanted to listen so we both talked until it was like 3AM.. we then decided that we both should just go to sleep..and we made a bet that when I got upstairs, my boyfriend would still be asleep and not wake up to give me a cuddle or have sex with me
I got upstairs and tried to wake him up but he was passed out. I stripped and got into bed. I messaged his friend and said that he was asleep and i was horny. He said he was too. So we joked around a bit and I said "well *boyfriend* cheated on me with you so I guess If I come down and suck your dick, that would make us even" he said something like "it wouldn't fit in your mouth" and I said "wanna bet?" and he dared me to come back downstairs. I put my dressing gown on and went down because i never refuse dares and I only wanted to mess with him.. he opened the door to the bedroom and let me in we cuddled for a long time and he said "I haven't had a cuddle in so long" I told him "it's okay. I'm here for as long as you need. You're my friend now and I care about you" he didn't really say anything after that.. I'm not sure if he was shocked that I completely forgiven him for making my boyfriend cheat on me or that he just didn't hear anyone say that to him before.. a while after, he said "you smell nice" I said thanks, you do too" then he said "Can I kiss you?" I was shocked and said "I'm not a cheat.. I can't do that to *boyfriend*" he said okay and we cuddled for longer.. I got really warm in my dressing gown and *boyfriend's friend* told me to take it off.. I said "I can't.. I'm not wearing anything underneath".. when I get really warm, I go all light-headed and dizzy and weak.. he took it off for me and uncovered me so my body temperature got back to normal.. I felt so weird.. I was so drunk.. he was touching me and massaging my breasts.. he said "I can't resist you" then started kissing me.. I did try to push him away and tell him to stop but then I just gave in when he put his penis inside me.. he was saying really nice things to me while we were doing it.. like "your body is amazing" and "*boyfriend* is a lucky guy" and "I really fancy you" ..
I feel like such an awful girlfriend.. I want to tell my boyfriend but I'm do scared of him leaving me.. I love him and I want a future with him.. the guilt and shame is all I feel.. it happened 2 nights ago.. *boyfriend's friend* is telling me to forget about it and it's "our secret".. please advise me on what to do?..