Hi!
But he is still eating and drinking normally and his weight is stable?
If he really couldn't pee, it would be excruciatingly painful and he would go downhill very quickly and dramatically once the urine backs up into the kidneys, as I know from a post-op experience of my husband's. It is a matter of hours and not days or weeks. He may just hold it in your presence and then make a huge pee once you have gone. Please be aware that not all piggies drink the same amount of water - in fact, it varies enormously individually. If he is one of the of the ones who doesn't drink or drinks only very little, then he won't be peeing all the time but when he does, his urine will be more concentrated so it comes out nevertheless. That is just the way his body works and will not impact on his kidney health or longevity, so no need to worry.
As a rule of thumb, as long as your boy is begging for his food, the internal conveyor belt that is his digestive system is running (pooing) and so is his plumbing (urination). Any blockages or problems tend to result in loss of weight/appetite. That is why life-long weighing (switching to weighing daily at the same time) is so important.
Please read all the links in this thread. You will find the practical detailed information in them very helpful and learn to understand more about how things are connected. We cannot explain everything in a post, hence why we link in the guides for all the tips, 'how to' and 'what' and 'why' aspect that you come up against.
All About Drinking And Bottles
Weight - Monitoring and Management
Squealing when pooing and peeing is generally a symptom of an infection, especially as your boys are a still a bit young for bladder stones (unless you are feeding a seriously high calcium diet).