He was fighting with another tom last week and on Sunday I noticed we was not himself. I brought him to the vet yesterday and he got an antibiotic and anti-inflammatory but today he had shallow breathing and wasn't eating or drinking. The vet gave him another antibiotic tonight but he is obviously very sick.

Has anyone been in this situation before and has any advice?

I have no advice, but just wanted to say how sorry I am, and hope your cat will get better.
Maybe another visit to the vets is needed?

no, sorry

take him back to the vet if you are not happy that he is not getting better - antibiotics take a wee while to get through the system I think so hopefully he/she will perk up soon!

It's very sad to say but he didn't make it.

Maybe I'll stop crying today but i doubt it very much ..

oh Im so sorry - you must be utterly devastated - sending hugs, not that it will help