I'm having with my mothers boyfriend??!?

I'm 16, and I'm having with my mothers boyfriend, she doesn't know but I do feel a bit bad! But the is amazing! He recently booked us a hotel room for the night, I told my mother that I was staying over a friends, we had all night, he turns me on when he says do u want me to bang that wet shaven tight pus sy? It was one of the best nights ever! We do lodes of adventurous things like, I've gave him oral when he was driving and he's fingered me while driving, we also done oral while my mother was upstairs in the shower. I know we should stop but the is amazing! He buys me y underwear and vibrators for me to use when he ain't there. I love it! I feel bad for my mother but I love the sex. What do I do!?