Should i be worried tht i drink at least 15 to 25 bottles of water a day and only output once or twice a day at the most and sometimes don't even go?

If your measurements: Are accurate & you're drinking 80+ oz water per day & only urinating 0-2 times per day (average volume per void is 8oz), the remaining water has to be going somewhere. If you're exercising a lot in a dry climate, the rest of the water could be lost thru sweat & breathing. Urine should be clear to very pale yellow. If dark, drink more water. Watch salt intake. See your doc if concerned.

See MD: Though water output is the most through urination, we also lose is through breathing, sweating and a very small amount usually through defecation. Still, it seems that your intake is out of proportion to your output unless you are exercising ANS sweating a tremendous amount. What may be more telling is the color - if it isn't light yellow or nearly clear then there is a problem. See your md.