This could be a lot of things. So I want to redirect your from cancer to possibly a parasite or an immune deficiency. My main reason for the redirection is to not scare you. Cancer is always a possibility, just make sure to schedule a doctors appointment ASAP and have your issues addressed.
Go to the ER if you have no insurance and get them to give you a colonoscopy. That could be colon cancer. Diarrhea should never last that long. My ex father-in-law died from it and that's not something you want to mess with.