If you don't already get a lot of sodium it could be a lack of sodium. I drink a lot of kava daily and double or even triple my sodium intake to keep up with kavas strong diuretic effect. I feel absolutely horrific if I don't make sure I'm getting enough sodium. I had no idea what was going on before I increased my sodium and what you describe sounds pretty similar. If I'm dehydrated and Don't have enough electrolytes the kava doesn't even give me any good feelings, just horrible hangover-like badness. Don't forget to make sure you get enough water as well if you do try to increase your sodium but not so much that you flush out all your electrolytes. Just try to pay attention to when you start to feel like it's all balanced. If that is the problem you should know pretty quickly after you increase your salt. Try eating some pickles or green olives during your sesh or drinking a Pedialyte maybe, I absolutely could not live without Pedialyte lol.