I Have A 6 Year Old. He Was Hospitalized Last

I have a 6 year old. He was hospitalized last year due an asthma attack and pneumonia. He does have an inhaler but he doesn't use it often. I have noticed lately that he gets tired wile speaking or reading. Sweats cold and coughs wile or after running and complains about his chest. He goes from happy to angry to being sad in seconds.