It is most likely due to inadequate thyroid hormone replacement after your thyroidectomy. Do you have copies of your blood test results. How much levothyroxine are you currently taking?
These seem reasonable doses although the blood tests will confirm. Sounds like you have IBS and it was a consequence of your thyroidectomy. I would try supplementing with magnesium for a few months, I use magnesium citrate but other forms are effective but not the oxide or hydroxide. Both hypo and hyper thyroidism can cause magnesium loss, it can take months to restore tissue levels of magnesium.
The thing with food intolerances, is we often don't realise we have them, until we cut them out and try to bring them back in. It's because we mostly just get used to feeling a bit rubbish, and also because symptoms take up to 3 days to show.
Around 75%of people with autoimmune thyroid disease struggle with gluten, while 50% struggle with Dairy and 50% with soya. To establish if you're one, cut them out for 30 days, then reintroduce 1 at a time, and wait 3 days to see if you have any side effects (incl. Headaches, rashes, insomnia, fatigue)
If your doctor is no help, I would also suggest you see a nutritionist, as they'll be able to help figure out what's going on with your gut, and advise on was to fix it. Are you in the UK? If so, you can find a qualified nutritional therapist via this site: bant.org.uk/bant/jsp/practi...
Nutritionist isn't a protected title, so anyone who's done a 5 minute internet degree can technically call themselves one. BANT only accept people who've obtained a university level degree in the subject.
Content on HealthUnlocked does not replace the relationship between you and doctors or other healthcare professionals nor the advice you receive from them.
Never delay seeking advice or dialling emergency services because of something that you have read on HealthUnlocked.