Allergies vs. Costo

My doctor is convinced my breathlessness or air hunger is just due to allergies. There's no clear trigger, antihistamines don't help, the air hunger comes and goes in random places/random times/random triggers. I've tested negative for all the big potential allergens I live with (grass, pets, dust, etc.) Cold season here so no pollen. I've tried 5 different antihistamines with no relief.

One nurse noted that she didn't think my ribs were expanding fully during deep breaths. Doctor ignored her. I've had heart and lung workups and scans and all the actual organs appear to be working. I get pain in my sternum but one doctor told me that's not possible and I must just be feeling gas pressure from overeating.

My oxygen levels are almost always perfect, it just feels like I can't pull in a big satisfying deep breath. Like something is lightly sitting on my chest and doesn't want to move so I can breathe.

Am I crazy to think my doctor might be wrong about it being allergies?