Autoimmune, celiac, vitamin def, thyroid,anemia all normal. still having dark circles, dry hair is thinning, dry skin, could it be pcos or low acid?

Dry thin hair& skin: Sounds like you've had all the proper blood work. I would make sure you get vit D and B checked. You could have an intolerance to gluten which would not show up on any lab test. The sx also sound like you maybe malnourished..have you been doing extreme dieting? I know when I diet everything is affected, and not right away. Try going gluten free, and drink water and tea..no soda. Feel better!