(1) that "thingy" you have there might be too long; (2) Her "thingy" might be too shallow (so the tip rams the entrance of the uterus when you thrust; (3) it might also be aggravated by the female having "cervicitis" (according to some friends, that's painful); (4) you might not have lubricated it properly; (5) her thingy might be wounded inside and that position might be exposing the wound to unnecessary friction (wound can be caused by sticking something foreign into her, too much use of latex, accidental scratching by the nail when you stick your finger in...