Hi Personally, I would alter take meds until I knew the cause, lots of blood tests etc. For thyroid start with TSH, T4 and Free T3 ,. Then recheck the other tests we list.
If you then think it is your thyroid, see an Endo , pick a good one yourself and then ask for a referral,. The reason is they are the most widely knowledgable of the specialities as a general Endo covers so much They can also do the only really good Adrenal tests, 24 hour urine test + cortisone, script at midnight, blood test at 9am Endo`s usually consider that the thyroid as good as possible first, if needed, then Adrenals if still needed...
I would also ask the GP to do LFT`s, liver, U`s and E`s , kidney, and also a FBC, full blood count. Ask for a print out of everything, + ranges very obvious then reading the results,useless any way without ranges as all Labs differ.. Liver and kidney and loads of things can cause these symptoms.It could also be Gall bladder, it is not classic for this, but need not be , it is autoimmune too. An ultra sound would show this, usually, not fool proof.Have you considered caeliac disease, autoimmune? The blood test is not reliable so, if you think it is this you ould need to try the diet ,strictly for 6 weeks and see.Not nice!