Sugar!! Please help me

I am 19w +1 atm and im exhausted .. I work full time as an accountant so lookin at the comp all the time n concentrating, no caffine but i hav replaced it with decaf n 2sugars about 4 a day, biscuits, chocolate, cake anythin to give me a bit of energy! But now im worried about gestional diabetes and weight gain ... Can anyone help me with something healthier to help me stay awake! Please help!!