I am going to try to answer your question.
I do not believe adding more fiber to your diet will improve your bowel movements. A lot of fiber can cause a lot of bloating and abdominal cramps.
Nortryptiline is a good medication for the treatment of IBS, you might need to go back on it. There are not too many things that can otherwise help you. Taking a probiotic can sometimes improve symptoms in people who have up to 6-7 bowel movements per day with a lot of gas. I personally recommend a probiotic called "Digestive Advantage".
If you are taking the probiotic and still experiencing bowel movements 3 times per day, again, I would recommend going back to the medicaiton which was controlling your symptoms before especially if it was not causing you any side effects. Stopping running will not have a profound effect on your irritable bowel (as a matter of fact, exercise is recommended for people with IBS).
I hope you find this information helpful. Please let me know if you have any other questions or need any additional clarification. I will be happy to assist.
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Best wishes and happy & healthy new year,