My cat was playing, eating and purring when he had the breathing problem. I had no idea it was that bad, but x-ray clearly showed that it was an emergency. I also thought that it was infection or something but so glad that I took him to the emergency vet. It's really scary to think that I could stay home and not knowing he was slowly dying in front of my eyes. Cats can mask pain so well. I really hope that you talk to a vet, so that you won't regret and feel guilt if worst happens. I really hope that it's not that bad, but from what you described it sounded kind of scary.