Diarrhea on your period

I'm on my period and this happens to me often where I get diarrhea with everything I eat. Any and everything makes my stomach queasy and within the hour I have to use the bathroom. I know it is possible I could have Endo because I have pelvic pain and vaginal pain a lot before and during my period. I'm not sure if it's related to that or something else. Plus idk if it is endo because the doc doesn't want to do a procedure unless b/c doesn't work. Anyway, does anyone else ever have constant diarrhea? Why does his happen?