Oh Leona...I know what you are going thru.
My Big Boy had the same thing. He did pass the stones and now eats Science Diet Prescription food. It can only be purchased at vets, and let me tell you, it's pricey, but it's worth it!
Both my cats eat it. Little Girl cat really doesn't need it, but there's no way I can seperate their food, and the vet says it's ok for her to eat too.
I totally understand about the cost. It's insane what they charge, but we do pay it for the love of our pets.
I'll keep good thoughts and prayers going that the stones break and pass with no problem...well, it'll hurt him a little, but other than that, once they are gone and you keep him on the special food, all will be fine. Just don't do what I did. Found UTI food in the grocery store cheaper and thought I would buy that. WRONG! They came back! So, only prescription food for him from now on. He's been eating it for the past 9 years and we've never had another problem.