Why do i always pee much less, hours or 1 day after i have drank caffeine? it's about half the amount as normal, but it completely returns to normal.

Usually the opposite: Caffeine, which is a stimulant, usually works as a diuretic and causes increased urinatiion after consumption. If your urine output returns to normal you may do well to avoid caffeine all together. If you are unable or unwilling to abstain from caffeine and you are still having problems, you could seek eval by a urologist to assess your voiding.