Is Bydurion the same thing as Metformin? If it is, I haven't noticed much of a difference in how it is changing my readings either. But it may take two months as it has to build up in your system. Maybe your medication has to do the same. As far as losing 40 in 2 months, your doctor might feel that was to fast of a weight lose for your body to handle in terms of controling your sugar.
Start weight when starting tracking with fitday:
314- Nov. 28, 2011
Current weight:293-Dec. 14, 2013
My Desirable weight: 125-160 (Lowest-Highest)
I'm just making lifestyle changes.