HI, I'm Dr Steve. I am sorry to hear that Charlie is having dificulties tonight. Can you tell me the last time he urinated?
I see you are offline. I will give you some thoughts that I have. Cats are usually very pain tolerant and if he is acting like he is in pain. there likely is something wrong. Some more common conditions that I see to cause distress in cats are injuries ( which it sounds like he doesn't have any noticeable ones at least) and urinary tract problems.
Urinary tract problems can include bladder infections which can cause pain and Bladder stones that can become lodged in the end of the penis. When this occurs it is very painful both at the end of the penis, but also in the abdomen where the bladder can become very full and distended from not being able to empty the bladder due to the stone blocking the penis.
With either of the urinary possibilities, there is usually frequent trips to the litter box due to the bladder spasms that can occur. With a bladder infection, there often is small amounts of urine produced each trip. With bladder stones, there are frequent trips to the litter box, often accompanied with crying or howling while trying to go , but no urine is produced.
If you think he may have the stone possibility, this can become an emergency due to back pressure on the kidneys from the full bladder. This can cause kidney failure.If he is not urinating normally and if you see him go to the box and not pass any urine he needs to be seen by a vet as soon as possible. they will tranquilize him and put a urinary catheter into the penis to break the stone loose and drain the bladder. This should be done even tonight at an er clinic if you suspect any blockage.
If he is passing urine then he may still have a bladder infection, but it is not as urgent as a bladder stone blockage. I will check throughout the rest of the night and tomorrow morning to see if he is passing urine. If you could let me know if he is having any of the urination symptoms I have described, then we can see if he has urine issues or other problems. Remember if he is not passing urine, then you don't want to wait for me. You need to get him to an er clinic as soon as possible. I hope this has helped. If it has would you please rate my answer. Thanks for the question. Have a nice night and good luck. If you have more questions, let me know and I will try to continue to help you.