11year old gets sick every 3 months. Abdomen pain near belly button. Feels nauseated, vomits mucous, last episode 3 months ago: lower GI bleed. Now again?

See GI doc. A number of things could cause these symptoms. A meckel's diverticulum comes to mind. This is an abnormal area in the intestine that occurs during fetal development. It can cause symptoms that come and go, including pain and GI bleeding. A doctor who specializes in the digestive tract (gastroenterologist) might be the right person to figure out what's going on. Ask your provider to refer you!