diabetes

So, I was about 30-35 pounds overweight when I got pregnant. My father recently told me that with pregnancy comes a heightened chance of getting diabetes. Is this true?? Because I am very scared, and I have been trying to eat healthy and walk and lose some poundage but im instead gaining more weight. :( 
***my doctor said she does not mind if I try to lose some weight but to not worry too much about it.***