Hi Smilen, I also suffer (or should I say suffered ) from Type 2 diabetes. It def sounds like low sugar to me. Speak to your DR, mine required a 5 day very low calorie diet early on in the process where they force the body to go into ketosis. All I was allowed was 9oz (3 morning 3 lunch and 3 dinner) of lean meat and two cups of chicken broth per day. At the end of the 5th day they measure your ketone levels to see if you follow instructions and confirm you can control yourself prior to surgery approval. I barely made it to the 5th day and I had a long talk with my DR. She immediately understood and for my 2 week pre op diet gave me a much more inclusive low fat low calorie but Protein rich menu. Diabetes isn't something they take lightly, they will make adjustments.
On the bright side, hang in there, I am 10 days post op and completely off my medicine since surgery date. My sugar levels have been steady in the 80s good luck!