Anti spasmodics????
Not sure if he is 'bumping into something' in there but he may be hitting something that sets off a chain reaction.
Sex stimulates the whole region and can have all sorts of different side effects...you can get 'honeymoon cystitis' which causes burning down there, leakage and all sorts of other goodies on 'normal' women...so us, with our rerouted biology and things that are pushed and pulled around in there we can get all sorts of post-coiatal side effects.
Is it just this once or is it every time? Is there also pain during sex? Is there one specific spot that hurts more during sex than another (I had stabbing pains on the right side that left me doubled over and breathless (not the good kind of breathless) and had me aching for hours post sex...turned out to be ovarian cysts...another time it was sterile abscesses in the cul-de-sac of Dougas (the peri-sacral zone I think) that had me throbbing for hours (again, not the good kind)...Most unusual pains are symptoms of something or another (not always bad or awful things)...so get it checked out, please.
(and don't stop having sex!)
sharon