Cat breathing heavily?

Our cat has suddenly started breathing very heavily and is just sitting in the corner of the lounge looking like he is trying to recover by not moving, just sitting. he is very quiet, but fully conscious, and was very lively as usual, about 4 hours ago. We think he may have swallowed a bee and been stung in the throat or maybe stomach, or maybe a small animal or bone (he does catch a lot of shrews and mice, for example). He is usually very fit and lively and it is very concerning to see him so still. could anyone give any advice please ......thank you