I dated a girl who liked to play that whole "stop, no" when she really just wanted it rough. Didn't have a safe word...so one time I was really pounding her from behind and she told me to stop...I thought she was playing and told her to STFU until I was done. Welllll...she really wasn't playing that day. I felt badly...but at least I came. Should have gone all in and gotten some anal....