Sex with your boyfriends friends

I told my boyfriend I wanted to try some new things in the bedroom I'm fairly new to this whole sex thing I lost my virginity last year and he's had sex a multiple times I asked him to tell me about the things he's tried and he went on and on about the things he's tried with passes girlfriends and he decided he wanted to try a fantasy gangbang with his friend and he doesn't understand why I don't feel comfortable with it! How would you feel, would you be up for it?

UPDATE: he’s having A baby by the girl he cheated on me with.