How long have you been counting carbs? Adaptation periods can suck for a while. 100g/day isn't very low, though... so unless you were really eating a lot of carbs before, it shouldn't be too big an adjustment.
Are you counting net carbs (subtracting fiber) or total? Because if you're eating a lot of fibrous veggies your net carb count might be quite a bit lower than your total.
I am low- to very low-carb all the time and I sleep just fine, but I have been doing that for a year, and everyone's a little different.