Was I raped by my step brother?

Long story short im 14 &hes 17. We got in an argument last night because he kept rubbing up on my inner thigh and I asked him to stop. Then I told him to f h ok mself and he slapped me and began to undress me and you know the rest. I told hom no and screamed but my younger siblings couldnt do anything. What should I do im stuck here for 2 more weeks with him. Should I tell my mom? Shes so happily married and I dont want to ruin that..again. What should I do?