My cat has chronic sinus infections every month or so. I put her on antiobiotics, she clears up, then it just comes right back. Starts with some discharge, always in her left nostril, then sneezing and heavy breathing with worse and worse discharge, then to her eye and finally right nostril. Got so bad last time she stopped eating and I had to take her to urgent care. She has been tested and found negative for FIV and any viral infections.

I'm not sure what to do at this point. I feel like giving her antibiotics is just a losing scenario. I've tried lysine supplements, making sure the place is clean including her litter and food areas, air purifiers, making sure her food is LID, etc. The vet wants to do a rhinoscopy because they think it's structural but that's like 5K to potentially find nothing. Cat is a rescue I've had for a year, the foster said she only saw a sinus issue once and it went away on its own and they had her like 2 months. I kind of want to get rid of her, but I feel bad about that (she's like 12). This is my first cat.

>pic related, my cat