Do check out the nutrition link. Depending on how intense you want to get, it's got information that can give you a general understanding, right to the basics you need to have a comprehensive understanding of your cat's needs.
Just reading your post and it sounds like what I am going through. They have not found blood in his urine but the crystals. My cat was blocked and they catheterized him for a few days and I have him on a special diet food prescription diet s/d which is supposed to help with the crystals. I just posted a comment myself about what is going on with my cat for any input because I dont know what to do anymore. They also have him on an antibiotic and want to check the urine again in 2 weeks. They say this is common in cats and worse for males. This week alone between his vet and the emergency one I have spent 600.00 Good luck to you
It isn't unusual (well, some) for a cat to sit/lay about in the litter box. While disturbing, it's not necessarily a sign of a problem.
Is there some sign of discharge that would suggest infection? It isn't wise to used antibiotics to recklessly. Recent studies show preventive antibiotic use can do more harm in the long run.
If you're concerned, try getting a second opinion. It's possible that you may need a more complex diet for your cat, beyond the science diet.
Is this a dry food or wet your vet gave you? Did you purchase it through the vet or store? I only ask becuase if it's through the vet, I'd definitely get a second opinion. I've got a link here I'll give you that talks in detail about kitty's complicated nutritional needs,
A good idea would be to get a urine ph balance and adjust diet accordingly using the below information to make sure kitty is properly balanced.
http://maxshouse.com/feline_nutrition.htm
My cat has blood in urine and vet said she had crystals. gave her science diet to eat, but I feel she needs a antibiotic . she would not give me any. She will sit for hours off and on in the liltter box without going. I am worried. HElp
Try the special diet. Ask at the pet food store, they'll direct you to good food choices. If the problem does recur, I'd consider getting a second opinion to be safe.