Hi I'm 12 wks pregnant and having fondant icing cravings, eaten 950g in 3 days.. how much damage have i done?

Hi I am extremely worried as have figured, too late I might add, that diabetes could be a potential problem, also is there such a thing as sugar poisoning? I don't mean to sound stupid or careless, I would never ever intentionally harm my baby and common sense tells me I may have.. this is my first pregnancy and am finding out all the do's and dont's now, any help or advice would be greatly appreciated. Thank you Haze xx