When having sex with my boyfriend, it feels like he is hitting against something. He said it feels like the tip of his penis is touching something like a knuckle that moves to the side under the pressure. After sex, I always have discomfort, mainly in my pelvic area. It lasts for 10 to 15 minutes and feels like the discomfort at the beginning of my period. Also, it makes me feel like I have to urinate. What is he hitting? Should I see a doctor?

--D.L.

You should see a doctor to rule out any significant problems, but what is most likely is that your boyfriend's penis is hitting your cervix. The cervix, otherwise known as the mouth of the womb, is located at the top of the vagina. If you insert your finger, you can feel it as a firm area; it feels almost like the tip of one's nose.

Because the cervix is part of the uterus, if the cervix is impacted during sex, the whole uterus is moved. This can be uncomfortable. Usually position changes can help alleviate this discomfort. Being on top allows you to control depth of penetration and is the position that works best for many women in your situation.

Discomfort may be a sign of prolapse, or dropping, of the uterus, a condition that most often occurs after childbirth, In such cases, one option is surgery -- either resuspension of the uterus or a hysterectomy, depending on the severity of the prolapse, your age and your desire for future pregnancy.