Is it normal to have diarrhea during my monthly cycle? Non stop diarrhea. What can I do to help stop it besides immodium.

Yes. Many women would have diarrhea associated with their periods especially if they have pelvic cramps. If the diarrhea is only occasional or isn't bothersome, you don't have to do anything, since you know it will resolve quickly. If you can predict when it's going to happen, you can start taking medications before symptoms start. If you have PMS with it, you may want to take NSAIDs.