What Could Cause Monthly Debilitating Right Groin Pain Years After Fallopian Tube Removal?

Hi there I had my Fallopian tubes removed 2.5 years ago. Then almost every month after that I have debilitating pain in my right groin area that usually lasts 1-2 days. I’ve had surgery to see what’s going on and they didn’t find anything. I can’t live like this losing days each month out of my life. Help