Is it normal that me and my step-mom are having sex?

I'm 18 she is 39. It started a couple days ago when my dad went away for the day. We were in her room watchin a movie when the thought of it even happening went thru my mind. I'm the kind of person that tries to act on my urges...so i moved my hand a lil closer to hers trying to not make it obvious that i was makin a move. when i finally got to were i wanted to be i jus let my hand chill there for a lil bit. Out of nowhere she started massaging my hand. One thing led to another...ya know makin out and all that. Well... we did have sex and it was amazing cause she could do so much! Anyways...i know she isn't related to me or anything...i was jus wondering if that was weird or anything?