Attitude and Nuts both have cat breath but it hasn't changed and every time I take them to the vet I ask how their teeth are(I'm sure the vets are sick of me asking considering Attitude seems always be at the vet, lol.) I have a good reason to stay on how their mouths are since FeLV+ cats have a higher risk of gum disease(and they can also get mouth/tongue ulcers, Attitude had a tongue ulcer at her first vet appointment) and so far so good. The best thing to do is the next time you have to see the vet ask about his/her teeth. My vet said how nice and pink Attitude's mouth was(in a good way) and since my vet always checks mouth/teeth as part of a normal exam(sick or well) yours should too. When they take a look just ask how the teeth look. Same as the above poster, make sure your cat is indeed healthy and go from there and check for changes in breath from there. It shouldn't be really bad though. If you can smell it when you aren't close(I have to lean forward and put my nose right next to the mouth when they yawn) or the smell makes you want to ralph or it's an overly sweet smell(diabetes) then I'd say it's a problem.
Taryn