Hi Dr. Kate,
My girlfriend (age 25) and I (age 24) seem to have a countdown clock running whenever we start. Let me elaborate: when we are fooling around, we always begin with foreplay, but after 10-15 minutes of foreplay she'll have cramping. This obviously puts an end to anything further. We have never made it past foreplay in the two years we've dated. Also, we are both virgins. What can I/she/we do to get our sex life going?
As arousal builds, so does muscle tension--not just in the genitalia, but all over. In your case, your girlfriend's muscles are getting so tense that they are cramping. You can try several things to reduce her amount of tension overall--give her a massage or take a hot bath together to relax her muscles before foreplay. She can even take ibuprofen (600 to 800mg) before bed. Once you're together and your girlfriend is aroused, bring her to orgasm--this will allow her muscles to unclamp, and some of the blood to start to leave her pelvis. Then you can try intercourse, which is more comfortable for many women after coming (maximum lubrication, maximum size to the vagina). If this works, you can try varing your foreplay to try and lengthen her arousal period.