Hi. I have had the similar prob. Only not every month. It happens about twice a year, and until recently, I thought it was a kidney stone. The pain radiated from the back to the front and got so severe, I had to go to the emergency room. They found an Ovarian Cyst. This can cause so much pain, and then go away. Be careful of surgeons. They can operate on you, and it still will not be solved. Go to a Gyno, that knows these types of probs. I feel for you. Best of luck.