Hi Skinmelin
The Thyroid issue is complicated, you can still be under active Thyroid with "in range" labs. Previously I did a longish post about it on here somewhere, try a search. This can cause weight to stick around the middle and extreme tiredness, puffy skin, dry skin, hair loss, and more.
It is difficult to piece things together when you know things are just not right, but keep at it ,as you know your body the best...and if things are out of kilter your body will tell you.
Have you had your Cortisol levels checked, might be a long shot , but having very thin arms and especially legs but holding weight around your tummy area does sound Cushingoid. High levels of Cortisol are produced by the Adrenal glands. Some of the symptoms can overlap with Diabetes ,and even be co-morbid. There is a Thyroid ,insulin, cortisol axis that is very common...one effect's the other. All hormones at the end of the day :roll:
Might be worth getting these checked and looking into Thyroid conditions again...Have you been checked for Diabetes?
Hope you get to the bottom of it ,it's not good when you feel unwell and can't find what it is, good luck.