The members here describe experiencing similar symptoms for a variety of reasons. Various tests and treatments have also been suggested. Here’s mine:
I have gastroparesis which is a neuropathy complication of diabetes. Basically food doesn’t pass from the stomach to the rest of the GI system; it sits there and rots. Initially it feels like constipation and like everything is clogged up until it eventually blows and is horrendous diarrhea. The test to diagnose is called a stomach emptying test. The treatment is small frequent snack like meals low in fiber.
I also have diverticulosis / diverticulitis that is little pouches lower down in the GI system / colon. Stool gets trapped in them causing constipation and when it finally evacuates it is hard little and marble or pebble sized. It is diagnosed by colonoscopy. The treatment for that is high fiber foods. In my case I think it is genetic. I had a parent and grandparent that both had that. It is an aggravation to have 2 different conditions at opposite ends of the GI system that respond best to very different treatments. My Dr. recommended that I experiment with small quantities of low, then high fiber foods to find out what works best for me. He also recommended a half dose (tablet) of Imodium daily to help deal with the unpredictable attacks of diarrhea.
The point is your symptoms could be caused by a number of things (maybe more than 1). Medical providers are necessary to order tests and recommend treatments. Your best bet might be your primary, an adult internal medicine doc or a gastroenterologist. You could present a list of the symptoms, time of occurrence and be ready to answer questions about your diet (types & quantities of food).