Hello & welcome, I am Dr. B, a licensed veterinarian and I would like to help you with today. I do apologize that your question was not answered before. Different experts come online at various times; I just came online, read about your wee one’s situation, and wanted to help.
Again I do apologize that my colleagues could not aid you sooner, but can you tell me:
How long has he had these signs?
Can he keep anything down?
Are his gums (not tongue) pink or pale/white? Moist or sticky?
If you press on his belly, does he have any discomfort, tenderness, or tensing?
Could he have eaten something he should not have (ie bones, toys, plants, chemicals, etc)?
Since you noted that he is breathing heavy, can you take a breathing rate for me (just count his breaths for 10 seconds + multiply that by 6)?