Sounds like it could be Interstitial Cystitis. Ask your doctor to be tested for this. My mother has it and the symptoms souns similar. Do you have to go the bathroom more frequently or have any burning?
Sorry I didn't read more carefully, since you already answered my questions. If you do in fact have Interstitial Cystitis, it will not go away on it's own. It is not curable at this point however there are many treatments available to control the symptoms. I would suggest doing some research on this condition and if you suspect it, bring it up to your doctor and possibly see a urologist. Some do not have much knowledge about IC, so try to find one who does. My mother took over 10 years to finally get a diagnosis and begin an effective treatment. By then, she had a very severe case.