Hi,
you should have a look at this thread:
http://www.hisandherhealth.com/ubb/ultimatebb.php?/topic/1/3555.html
It is another woman with your problem and I just replied to it as I have this problem too. There is a whole thread on this in the men's health forum. I posted the link in my reply to that post. I have found doctor's unable to help and more than one has told me this is a psychological problem, which is enough to make me depressed as I KNOW 100% it's not. It seems that doctor's don't have the answer, but it would be worth checking in case you find a good one. If so, please please share your solutions!