morning sickness & weight gain

If I am constantly keeping my tummy full I feel a lot less sick. I just get nausea so far, no barfing. 6w 5d. My cures have been Ginger Apple Juice (12 oz), rice crackers, and fruits (1-2 a day). I typically don't consume so much sugar, with the 100% juice and the fruits, so I'm worried about immediate weight gain and setting up myself for gestational diabetes. I'm not really concerned about looking fat or anything like that - just health of the little one. Should I be concerned this early? Or just fight the sickness until I get through it? Or find something else? 

My bmi is pretty low like 18 or 19 now so I'm not overweight or anything now.