Have Cat Questions? Ask a Cat Vet Online.
I am sorry to hear you are worried about Bob. My name is Rebecca. I am a veterinarian and will do my best to help.
A UTI is possible. He is a bit young to have diabetes or kidney disease, but these are also things we check for in cats that are not urinating normally. He might have sand or crystals in his urine, or stone in his bladder.
I would start by having a urinalysis done. If you can catch a urine sample you can take it to your veterinarian, or you can take Bob to the vet to collect a sample. Your vet might be able to dispense NoSorb beads for you to use at home to collect a sample.
Let me know what other questions you have.
Is he neutered? I forgot to ask. If he is not then that may be the reason.