I have been craving salt and drinking a lot of water as well. According to the Brewer diet this is good and normal for your body and helps with the rapid blood volume expansion of the second trimester. Salting to taste and adequate fluids in your diet actually protect you from pregnancy induced hypertension. From what I understand, salt, fluid, protein (80g-100g per day) and adequate vitamins from food sources, like leafy greens, beans, oranges and other vegetables and fruits, provides your liver with the resources it needs, otherwise water retention and high blood pressure result.
If you feel more nausea than normal, extreme irritability or have odd fruity breath then you may want to contact your doctor, as those are signs of too much blood sugar. Otherwise, if you feel ok, then it sounds like what you are feeling might be normal!