Im no expert in gestastional diabetes (but i have had type 1 for 5 years) so first of all i would ask your doctor. you should be being closely monitored during your pregnancy.
Im not surprised your blood sugars have changed though, i would expect this with all the changes that happen during pregnancy. keep closely monitoring you might have to have more snacks to keep your blood sugars up, or maybe wake up in the night and test to see whats happening.
I always feel quite bad for ladys with gestational diabetes. Diabetes is a condition that takes months to get the hang of, and of course your expected to get perfect results straight away!
Id get advice from the doctor/diabetic nurse before adjusting any insulin doses. Test regularly in the meantime and have a small snack if blood sugars are low.
x