Your water intake of 3-4 liters only covers your exhaled breath. Let me ask how dark your urine is. Coloration is the first sign of dehydration, not intake, and not oral thirst. Your urine should be clear or very near.
I weish 180-190, nearly 90 kilos, and I drink over 1 gallon through the course of a day. If I drink as little as 4 liters (Half a gallon) my urine gets dark.
I suggest more water, contingnent on color of your urine.