GD. Should I be worried?

I just learned I have gestational diabetes, I have been keeping track of my blood glucose level and it is always high. Highlighter in oranges are high, in green is right there on the limit. My doctor said if I cannot control my sugar with diet, I will take medicine for it. 
What kind medicine is used to stablish glucose?  
What I'm doing wrong on my diet? 
Thanks.