Is dry humping a sin?

I'm 18 and I have a boyfriend so last night we were at his place and kissed and it got pretty heated, my mom said I have to wait until I'm married or else having sex is a sin (she's a very religious Christian and my father is a pastor, I am Christian too) but we were caught up in the moment and I started grinding on him and he grinded on me and I think I climaxed. Now I feel really bad is that a sin? I'm scared to tell my mom.