It sounds like your cat has a urethral obstruction, aka "blocked cat." This is a very serious condition in male cats where crystals that form in the bladder get lodged in the urethra as it travels through the penis causing urinary obstruction. This leads to distention of the bladder, pain, build up of toxic metabolites, lethargy, vomiting and death if not treated quickly.
The diagnosis is made on palpation of the bladder as these cats will have a large, firm painful bladder.
Treatment is fairly aggressive, and without this treatment tonight he may die.
> First bloodwork is checked to see where his kidney
values are and where his Potassium is
> He will then be anesthetized to be "unblocked" using a firm urinary catheter
> He will then need to be placed on IV fluids and have a soft urinary catheter in place for 24-48 hours to monitor urine output and to keep up with his post-obstructive diuresis.
> Once the catheter is pulled and he is urinating normally he should be able to go home.
You need to get him to the local ER vet or your regular vet if they are open to get this resolved.
I hope this helps, let me know if you have any other questions.