This was happening to me for a little while too. I started drinking more electrolytes during fasting and eating meals more slowly. If that doesn’t work than maybe switch back to 18:6 or talk to your doctor to see what they think.
Does it happen when you eat certain things? I can get nauseous when eating as well. I usually have to eat food in a certain order and this helps. Example for me: I cannot eat almonds or any type of nut on an empty stomach without getting sick.