Gestational diabetes

JTJKH
I found out today I have gestational diabetes at 30 weeks.  I am so disappointed in myself! I'm taking it really hard and blaming myself for something I know is 50% my fault 50% not my fault.
I go tomorrow for diabetic counseling.  I'm worried I'm going to gain a lot of weight and have a big baby. 
Do any other ladies have GD?