Hello again producerchick.
Auntjudyg is right...this could be classic Diverticulitis. I have a couple of recommendations for you...
First of all, you will want to rule out anything more serious. Insist on every test in the book, starting with a colonoscopy (it is a breeze). If your gyn or family prac won't accommodate this, find someone who will. A good gastroenterologist referred by a Doctor you trust might be in order. You will want your lower left side thoroughly mapped because the source of your problems may be in your colon - or maybe not.
If your gyn does not take your increased pain and discomfort seriously enough to investigate the problem thoroughly, find a new gyn. If you have to, keep changing until you get a solid explanation.