diarrhea related to medication

i took a thyroid medication for hypothyroidism for twenty years with no problems.  i was healthy.  then the manufacturer stopped making the medication, and this was the only place that made it.   for the last two years i have been given prescriptions for other thyroid medications---none of them has worked out for me.   my reaction to all these meds has been diarrhea.  now i have figured out that the diarrhea is related to the thyroid medication and, consequently, to the type of foods i eat.  i can no longer eat any meat, chicken or fish.  they all cause diarrhea.  so  
now i eat only high fiber foods in very small meals throughout the day, and have had to turn into a vegetarian to get some control over the diarrhea.

what seems to be going on here medically?  i went from being healthy to being very ill. thanks for your help.

[mammo]

If you haven't see a Gastroenterologist to determine if there is more to this than your medication....you should.