This might sound weird but it depends on the headache. I have used Nene with good effects for almost anything I've had wrong with me even when you'd think it would be the last thing you would need, stomach ache, headache, muscle aches, cold and flu, you name it. If the headache is even partly due to dehydration then kava is only ever going to make it worse. I'd imagine that if you've drunk 2 gallons of water you may well be dehydrated anyway if you've not taken in any electrolytes with it. When I first started drinking kava I would drink so much water and I couldn't figure out why I still felt like crap. Look into some salt tablets and some b vitamins. Those two have really helped me. In theory ibuprofen is safe to take with kava where paracetamol (or whatever you call it) is not because ibuprofen is broken down differently (different pathways in the liver?). I've used ibuprofen for a bad tooth during the day and had kava in the evening and been fine.