Gestational diabetes

Soooo my Doctor is pretty convinced that I have gestational diabetes. Even though I passed my glucose test while on metformin. I am pregnant with twins. But the plan of attack is I have to check my glucose twice a day for the next few weeks alternating times each day and try to walk a little bit each day. She does not want me restricting my diet or exercising to much.  I have already lost over 25lbs due to my morning sickness. When I go back we will review the numbers and go from there. Anyone been through this before?! She told me if my metformin does a good job of controlling my glucose I wouldn't need insulin.