Somebody talk me off a ledge?

I finally got the cat I've wanted so badly for years and years. He's under six months old. I've had him less than 2 weeks and he's already been diagnosed with a URI, bladder crystals (Rx food for life) and a UTI. I was assured he was healthy, but he was coughing the day I took him home. ER vet said bladder/UTI issues have been brewing for awhile. I'm so sad and the cat is so miserable. I need somebody to talk some sense into me before I freak out at this breeder because I'm not thinking so rationally right now. Does this sound even remotely par for the course?