Ummmmmm...have you talked to a LLL Leader about weaning? We have several auto-immune diseases in our family, including diabetes, and it has actually been proven through replicated studies that breastfeeding often puts a breastfeeding mother's diabetes into remission. 99% of the time, when a doc says to wean, it's because they simply don't KNOW, because we have such s formula feeding society. It can be more difficult, until you get accustomed to your new metabolism, to get your sugar in order, but it CAN be done, and once it becomes your new norm, it is generally much easier to keep your sugar under control if you haven't gone into complete remission.
Also important is the fact that auto-immune diseases can run in families, and breastfeeding protects BABIES from becoming children or adults with diabetes and other auto-immune disorders...so if you can find a way to continue to nurse your baby, it can keep them from suffering from this as well. No gaurantee, but a stronger possibility.
Again, I would contact your local LLL, and ask them to put you in contact with the Professional Liason Department (or PL department). They will have access to the most recent and the most relevant research, and can share it with you.
I hope this helps.