There could be a few possible causes for your recurrent abdominal pain.
It is a good idea to be checked for chronic form of appendicitis.
Since the pain is reappearing almost every month, it could be related to your genital organs and their change through menstrual period.
In other words, you may have ovarian cysts or ovarian endometriosis.
Abdominal pain in the lower right area, and diarrhea should raise suspicious for bowel inflammatory disease like Crohn's disease, too.
Best wishes!