For Almost 3 Years I Have Been Having A Burning/stinging

For almost 3 years I have been having a burning/stinging pain in my lower right abdomen before, during, and a couple days after my period. I cannot stand to be pushed there and only feel a little more comfort sitting but without movement. Even coughing or sneezing makes it worse. It used to come and go really fast just strucks me but this year it stays and gets worse and then lessens in seconds but again in seconds gets worse and lessens. I've been to numerous doctors and hospitals and no luck. Nothing wrong with my appendix or not found anything wrong. It isn't cramping I have that apart from burning stinging pain on my stomach. I have 3 c-sections and it only started almost 2 years after my last child. What could it possibly be?