Try to heal the celiac's first. I would start with magnesium. There are also tons of things out there that are natural that can help you heal your colon. Off the top of my head...Omega 3 and a substance called l-glutamine that can be found in Bone Broth (as in boiling chickens and making chicken soup), cabbage and garbanzo beans.
https://badgut.org/information-centre/health-nutrition/glutamine/
https://www.furtherfood.com/bone-broth-diet-helped-heal-celiac-disease-treating-inflammation/
My heart is breaking when is see people struggling with some of these issues, some of which can be fixed as easily as going to the grocery store and a good quality multivitamin.

If you're taking Vitamin D and not absorbing it, try adding in magnesium. Start slow (half the dose) with a non- acidic form like citrate or oxide and experiment from there.

https://jaoa.org/article.aspx?articleid=2673882 Kinda' technical...sorry.

Spend some time on the internet looking for easy and alternative cures. They're out there.