Have you tried eating a high fat snack shortly before bed? Like a handful of almonds? I had gestational diabetes and my nutritionist swore by this method to keep blood Sugar steady overnight. It really seemed to work for me. After the babies (i had twins!) stopped nursing, I also added a berry based supplement from http://www.naturalsleepformula.net.
I sleep through the night without trouble now, even though I ended up with post-gestational type 2 diabetes (controlled by diet and exercise). I wish you all the luck in the world!