Is there something wrong with my cat?

First you need to make sure that he is urinating. A male cat that is not urinating is not good and needs medical attention immediately. This is a life or death situation. Alot of people think that their cat is constipated or has diahrea when they are actually not urinating and it is to the point of diahrrea. Sometime when they have blood in their stool its because the diahrrea has turned into colitis and this needs to be checked by a doctor. they have medication that they would give him for this. Please take him to a vet.m