Do not self treat and talk to your doctor now.
Any change in stool habits warrants a colonoscopy, unless you have had one in the last 10 years...at age 70 is typical.
We do not diagnose, treat or replace your doctor on line.
Simply adding fiber is not adequate.
It is not likely if your thyroid has been controlled that this is from thyroid. That said, TSH should be between .3 and 3. Some say 2.5.
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