My kitty has stopped eating as well, several times, and we have gone through a bunch of different options that have worked out for a while.
Here are the suggestions I can provide from my experience:

1. make sure the vet does a THOROUGH inspection of her teeth. If there is any redness or black around the gum lines, then her teeth could be the culprit.
2. Blood tests - as stated before check her thyroid, kidney, CBC levels, and liver. Something could not be working right, making her nausea.
3. Ask your vet about a appetite stimulant -my kitty has been on two (the names have escaped me, but send me a private message if you want the names and i'll go look), which have had moderate results. The one she takes a 1/4 of a pill for 4 days, the other she gets every 12 hours as needed.
4. Switch your foods. If you can temp her to eat with new foods give it a try. Try different, smelly, canned foods -the ones that come in the pouches with gravy worked awhile with Sydney. Also try vanilla ice cream and yogurt. I was told by others that these are high in fat content and can help put on some weight on your kitty. Watch for diarrhea -you can get anti-diarrhea medicine from the vet if this is occurring as well. Another great source is baby food. This is what my cat is currently eating. I have been getting the infant chicken in chicken broth. You can also try fresh shrimp or freshly cooked chicken breast.
5. If her stomach is hurting her (increase in acid) then ask your vet about Famotadine (also known as Pepsid complete). It coats the stomach, and decreases the acid amount.
6. Corticosteroids, like prednisone, are also known for increasing ones appetite. WHen Sydney was first diagnosed with cancer, we were giving her so much food because we were afraid of her not eating because of the chemo, and surely enough the prednisone increased her appetite and she gained 2 lbs! It may be an option you can discuss with your vet


I hope that your baby begins to eat soon. I can personally say I know exactly how nerve wrecking it feels when our babies don't eat. Just keep up the hope and stay in contact with your vet.