Diet soda is bad for you AND baby. Not only is it sweetened with either Splenda (which contains chlorine and bleach) but it also contains chemicals like phenylalanine and aspartame. Phenylalanine is what makes the soda diet, it's known for being the cause of breast and other serious cancers while aspartame is another artificial sweetener known for being the cause of cancer and kidney malfunctions. The best advice I can give you is try to ween yourself off of the diet sodas. I've found that decaf tea isn't as terrible as I expected but I still drink water like a camel.
Lol just drink water that's room temperature. I started doing that and now I drink 2 liters or more a day. Or get those little flavor things you put in water.