Help boyfriend trouble i dont know what to do!!!!!!!?

me and my bf where making out in his room last night he has a couch in his room well he was sitting down and i was straddeling him well we were grinding and we had no intentions of sex we do this all the time well in the middle of all this he grabs my butt and when we start getting into it like we always do his mom walks in and freaks out wha do i do and is there another way for us to makeout without her freaking out if she catches us