Hope you are ok with the celiac problem. I'd have to research this condition, never heard of it before. My opinion is that anything we ingest has potential cause for mental change, however significant. Depression is caused by a wide variety of reasons, so it's hard to pinpoint the exact cause.
My personality has remained constant from my standpoint. When I ask about how I was to family who knew me as a kid, my mom stated I always had lots of friends and was extraverted prior to puberty time of life (she has no idea what happened to me ) and my sister said I was always a "depresso". I think their perspective was highly subjective, but w/e. From my own vantage point, I see how I could have more of an extraverted dominant personality, in a deep way, meaning I could be xnfp, rather than infx, and this may be my deep rooted problem with socialization, which I've always just chalked up to bad parenting. I do wonder if I were a pure MB type, especially infj or infp why my creative output is so low. Then I get angry with myself, so I try not to go in that direction.
Typology has its glitches. First advice I would give you is not stress over your disease, this may make things worse. Whoever you are is what you should focus on, if you have a desire to be closer to others, do it. If you enjoy your introversion then truly be with it and enjoy what it offers. Noone ime is obligated to remain just one way throughout life. Personally, whichever type I was to begin with, now that I'm older, being introverted is WONderful. Wish I realized this sooner, but wth.