Feline Question: Our cat has been wheezing, and losing weight---> Read more please!!!!!?

We've had this cat for around 3 years and it was originally a stray. Our cat has always had an occasional coughing fit when scared or active because he has asthma but our vet never put him on anything for it. Recently, we have noticed he is losing weight and his breathing sounds congested or wheezing a lot. We are taking him to the vet Wednesday but what does this sound like??? He eats like a PIG! XD