Monthly, debilitating pain in esophagus

I was diagnosed with achalasia and had a very successful, life saving surgery. However, 2 years later I still get horrid, sharp pain approximately 1x per month. I’ve seen three specialists and they are all certain it is not Achalasia, do not know what is causing the pain. They’ve tested my pancreas, gallbladder, etc- I feel like I’ve done every possible test. I have two questions- have any women had endometriosis outside the uterus? One nurse suggested to me that could be it, but no one else seems to think much of it. Given the monthly episode; however, I am curious. Somewhat related- has anyone used magnesium for pain? Supplements or topical? Does it work? Are there side effects?