Abnormal breathing otherwise ok

I do plan to bring my cat to the vet soon as i can, he is due for his checkup anyway. But my 1 year old. recently started breathing abnormally. hes still eating and drinking fine, still a ball of energy and theres no other symptoms such as anything from nose or eyes and so on. he does seem to be breathing from the abdomen. he has coughed as if we had a hairball but no fluids or anything has come out. And this morning when i came home from work, he seemed to be doing better then he started to run around and it started up again. any ideas, or suggestions would be appreciated.
thanks
april