.Lynda, Your question is very involved and there is no simple answer to all your queries on a mobile forum. I suggest you seek private consultation with a qualified Dietitian. Levothyroxin and fiber have no relationship. From your symptoms it sounds like your medication may need adjustment. The IBS or irritable bowel syndrome requires specialized medical nutritional therapy/counseling. General guidelines for IBS - individualized diet, limit lactose, increase water soluble fiber - I suggest adding oatmeal in the am and choosing oat based products, drink 8 glasses water per day, use peppermint oil for gas, food intolerances should be identified through keeping a food/symptom diary, limit wheat products, get rid of fructose as much as possible (no juices,fresh fruit only, read labels for high fructose corn syrup), and finally, try taking melatonin for a short time to try to retrain your circadian sleep cycle. Don t take for too long as it will cut down on your body s own production like any other hormone. Personalized consults are available here directly from a specific provider, specialist for a specific category or general from anyone here. More comprehensive instructions can be given there that cannot be provided here. Or, seek advice from any local qualified Dietitian for more specific advice. Regards, Kathryn J. Shattler, MS,RDN