My 9 year old cat has been very lethargic today. I haven't seen him eat nor drink and I'm very worried. He's had urinary problems in the past and I'm scared that it has come back. Also, his belly looks a little bloated. I am going to bring him to the vet but I can't until Friday morning, is there anything I could do in the meantime to comfort him?

Take a marker and mark his bowl at the water line. Also I would only put a small amount of litter in the pan. This would be easier to measure the amount of urine he is putting out. You could weigh the litter and the pan when it is fresh and then at the end of the day measure it when it has been used. I mostly go by the wetness of the litter.
If he is not drinking then you really need to take him in. Also if his urine out put stops or get very low you will want to take him in.