And don't forget to be safe when it comes to grabbing hair, or throats and stuff. Have fun, but use safe techniques. ![Happy](images/smilies/big/Happy.gif)
Oh, and girls are different sizes just like men. I wonder if he's hitting your cervix. With the standing-man-behind position, you get real deep penetration, it's possible an average man might hit the woman's cervix. Just a possibility.
I have a long time interest in psychology, specializing in relationship dynamics for 30 years.
(Please note, we give the best advice we can based on the information given in a post. For better advice, please include the age of all romantic partners.)