What is wrong with my cat

In case it's relevant, my cat was born under my house from a stray cat. We found him when he was about a week old. When he was about 6 weeks old we kept him inside full time and he's never let outside. Since he was about a month old he's had a wheeze whenever he breathes. He's 6 months old now and he has good and bad days. On his bad days, he can barely breathe through all his snot and he has episodes of sneezing repeatedly for about 45 seconds. I've taken him to the vet over 10 times in the last 6 months. So far he's been on clindamycin, amoxicillin, clavamox, panacur, veraflox, chlorpheniramine, viralys gel, and azithromycin. I've been to two different vets and both have told me they're out of options since none of those have helped. I bought a humidifier, I've tried having him in the bathroom with hot water running for the steam and nothing helps him. He doesn't have a lot of bad days, he seems like a normal cat except for the constant wheeze noise. But on his bad days I get so scared because he looks like he's dying and he stops breathing sometimes. When he first had the wheeze, he never sneezed or had any snot, it was just in the last month or two that he started sneezing and having a lot of snot. We have to wipe his nose multiple times a day and he still drips snot everywhere. Two vets have told me they're out of options and I just don't know what to do with him anymore. Any suggestions for what could be wrong with him? He was tested for FIV and feline leukemia and they were negative

Hello!  I think it's odd that two vets have told you they're out of options with no further information or comeback.  Do they have a diagnosis or small list of possible diagnoses?  If this is in the UK, I would conclude that either 1) there's something 'different' here and that a specialist may be needed to identify and treat it or 2) They have identified a chronic disease and are treating it to the best of their ability, particularly when it flares up, but the treatment isn't keeping on top to of the illness.  More regular treatment may be required for optimal quality of life - perhaps more frequent repeat visits to the vets are needed.   The liklihood if it recurring needs to be raised at the follow-up, along with possible preventive measure.  If this isn't going anywhere then perhaps a specialist can help  3) Depending on the (working) diagnosis, I wonder if there is space for regular inhalation treatment for example?  These are all things to think about with your vet, perhaps now - before it flares up again. Best of luck

Going back to that inhalation treatment - it doesn't sound as if it helps at all.  Maybe a specialist or your vet could take a close look at what you're doing and pin down what that is?    Or whether there are other decongestant drugs that might help?  Or maybe for a cat with that disease and that shape of nose, for example (I don't know your specifics but the vets will) they really do feel that there is nothing else you could be doing differently.  Your specialist is the best to make that call, because they will know more about that subject than their a general practice vet ever can.  I hope that something in all of this gives you some ideas!