Really important to have your Folate, Ferritin, Vit D, B12 tested along with thyroid antibodies and as you have PTSD I'd get your adrenals tested if they haven't already done this. I'd guess with all that stress they are bound to have been affected. My son was a marine and got a medical discharge after serving in Afghanistan, he was in a bad place for a while but then took a meditation course which helped enormously. I can get the details if you like? You in the UK? He still meditates now and finds it hugely beneficial. He also changed his diet which helped with stress and inflammation.
Thyroid plus 11,12&15 are all good comprehensive tests and they also have a 24 hr saliva test for cortisol. Not cheap but worth it to get to the bottom of what's going on.
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Please get hold of your blood results (they are yours) and post on here and then any future results you get.
You could also try quitting gluten and dairy and eating more of a paleo diet for a while. Should help with stress and inflammation.
You could also try a good probiotic, one with multiple strains, I'm guessing your microbiome will be completely upset too.