No worry. I was a diabetic during pregnacy, and was taking insulin to control sugar level. My baby is very healthy and looks bigger than 18 months old although she is only 11 months.
I think this could be quite common, but controling food consumption is very important; otherwise your baby might be too much overweight, which is not necessarily good.
I had gestational diabetes in my third trimester as well. Dependson the severity of your blood sugar level, you should undergo :
1) physical exercises, walking for at least 40 minutes every day;
2) food control ;
3) daily blood sugar monitoring ;
4) set up a plan with your OB together that is working for youself.