HELP!!!

So lost my virginity to my boyfriend a while ago, and we've had sex a little more than a hand full of times. Ive been on top once and it hurt. I just tried going on top again and it hurt again. We had to stop because parents came home so naturally I went to the bathroom to wipe, and there was some blood, kind of as if I spotted on my period my I know it's not my period because I don't get it for at least another week. Why did I bleed, I haven't any other time we've had sex because I always wipe after. SOMEONE HELP
Also, it doesn't hurt if he's on top