Why have my cats habits changed?

Question
I have a male cat that is about 4 years old. He has been litter boxed trained ever since we got him.i have never had to clean up after him once. In the past few weeks i have noticed something strange going on with him. He was behind a table and looked like he was trying to use the floor instead of his litter box. I picked him up to take him to his box and he let out this hurt cry, i put him in the room with his box, he came out and went to several places and just stood ,like he was trying to go, he looked like he was in a trance or state of confusion. The next day he was fine. Today the same thing happened again, he went to several places including the bath tub scratching like it was a box, I left him in there for 10min to see what would happen, he went and it was like a drop of yellow liquid,that was all. He usually sleeps all day, and did not sleep at all today,and he lets out those hurt crys. I know something seems wrong and I am not sure what to do-He is a inside cat, so it would be very hard to try to get him to the vet,and they  are always so busy. Any thoughts you may have to help this situation would be appreciated.

Answer
Val,

This kitty should see a vet ASAP, he may be experiencing painful urination due to a bladder infection or he could even have stones/crystals that block his urinary tract from time to time. If these stones fully blocked his urinary tract he would likely die an excruciating death within 24 hours if he didn't receive treatment because urine would eventually wash back up into his kidneys when his bladder became overly full and he would either die from his bladder rupturing or his kidneys shutting down completely due to being exposed to toxins that they've previously tried to send out of the body in the urine. The behaviour his exhibiting is his way of communicating with you and telling you that he is in serious pain - cats are typically very stoic and they will hide symptoms of illness and any kind of pain until they can't bear it any longer, it's a defense mechanism that's allowed them to survive for thousands of years without becoming lunch for bigger, stronger predators and being wiped out as a species. If you have a cat carrier try bringing it down where your kitty can easily get into and out of it, place a soft towel or small blanket inside for comfort and book the vet appointment for the earliest possible date - be sure to tell the technician or receptionist what symptoms this kitty has because his symptoms are indicative of a veterinary emergency and you may be able to get him in the same day you call. In the event that you don't have a cat carrier it would be wise to invest in one large enough for your kitty to comfortably walk in, turn around and lay down without being cramped into a smaller space than would be comfortable for him. The other alternative would be to check your local phone listings to see if there are any on call mobile vets who would come and check your kitty out and make recommendations based on their findings but these services tend to be very expensive and are very rarely associated with a stationary clinic so in all likelihood you'd be spending the money on an expensive service that would refer you to the nearest emergency clinic. I suspect that your kitty will need to be hospitalized for at least a week in a full service veterinary hospital for diagnosis and treatment of his medical issues at this point. If you have any further cat related questions or concerns I'd be more than happy to help you out to the best of my ability.