--obviously, one would think the diabetes would be the first place to look, and I am sorry that you are experiencing this so young, but diabetic neruopathy, especially painful small-fiber types, can present at any time along the progression to diabetes--even with impaired glucose tolerance (pre-diabetes, among people who may go on to develop Type II, so one doesn't even need a frank diabetes diagnosis to experience it).

But what you also report are a cluster of autoimmune situations--along with the Type I--any of which could have neuropathy as a component. Certainly gluten problems/celiac are linked with neuropathy, as are a number of other autoimmune conditions besides Type I. (And autoimmune conditions often come in clusters.)

Have you been to major academic/teaching hospitals during this process? How extensive a work-up into neuropathy possibilities have you had? (There is a tendency among clinicians to assume if you have neuropathy and diabetes that the diabetes is DEFINITELY the cause.)