I've struggled with horrible bloating, belching and nausea for about 3 years, which got slightly better with thyroid medication and antacids, but in the end it was all because of an "intolerance" to all starches in my case. My doctor has no real idea what might be the cause, we thought it might be celiac disease but I tested negative (and it happen with anything from grains to potatoes). Took me forever to find out because I did an "elimination diet" that consisted of chicken and... white rice. Which made me as sick as ever.

Long story short I strongly suggest that you try doing an elimination diet, allergy tests, low FODMAP diet, paleo diet (which did the trick for me) or just experiment with food in general. Took me 2-3 weeks of no grains and starches in general to feel better. 29yo male btw.

For what it's worth, I say it could be thyroid-related, but I'd look somewhere else first.

I've always had problems with bloating and constipation. I literally could toxic-fart 2x every minute, TMI. Two weeks ago I went gluten free, I immediately dropped five pounds, my stomach is flat and no it longer feels like a dough ball and now I fart like 5x a day. My lymph nodes are no longer swollen and I have more energy. The gut and the brain are closely connected and the gut is often linked to autoimmune diseases. I was super stubborn about not changing my lifestyle but in these two weeks I have seen how eliminating one thing from my life has caused big changes. I recommend looking into "leaky gut" and doing your own research on gluten and hypothyroidism, I will say that the research is mixed, but why not try something different. If you don't notice a change, well fine, at least you tried. Eliminate gluten seemed daunting to me, but now days there's gluten free pasta, flours, and even desserts. Keep us updated!