Hi Meghan, welcome to the board.

Twice a week probably won't hurt. One caution with the sweetener, the packets of powder usually contain about 0.8 grams of carbohydrate, so do count that.

The nut milk is "technically" a no-no, but probably only because the stuff wasn't common in the marketplace when Atkins wrote his books. Just make sure to get the sugar free stuff, it should say a gram or less carbohydrate per cup.