Having sex while i'm asleep?

OK, so I sleepwalk alot, but my girlfriend doesn't mind it. But there was this one night (a few nights actually) where I was sleepwalking, but this time, I had sex with her while sleepwalking! I went right back to sleep afterwards and I didn't know anything about it until I woke up with a boner and my girfriend commenting on it. Is this normal?