If your boy is eating and drinking just fine and his poos are looking healthy and normal, then he is peeing OK and is obviously getting enough fluid. So please don't worry! A guinea pig that has problems with peeing won't drink or eat and is a very ill piggy indeed!
PS: We try our best to answer any threads in the health/illness as promptly as possible, so it is not necessary to ask for help as you will get it anyway, but you can help us a lot by putting the nature of your problem in the title, so our members can attend to the most serious issues and the ones in which they have the most experience first in their free time.