christine.....you seem to have had an exhaustive gynae investigation, but not a Urological one.
Perhaps a urologist would do a cystoscopy and urethroscopy, to eliminate any bladder abnormalities.
In direct answer to ypour question, I cannot see the relevance of he question unless he suspected a cystocoel (weakness of the vaginal wall) but he would obviously have picked that up during examination.
You can't go on like this, ask your GP if you could be refered to a Urologist.