Hi Laura -
It sounds like your child could have a variety of different things. First he has some type of infection if he has fevers - maybe this hasn't been resolved yet. Once you have pneumonia it can return.
Second does your child have any allergies to (dust, pollen, pets etc.) Children that have alleries - tend to have a lot of mucous production and then are more prone to infections.
Third - your child could have just plain asthma - or could have an allergy induced asthma - or might just be having trouble breathing from having pneumonia.
It sounds like your child has had a tough time this winter, but let me give you a little advice. I am not sure where you live but if you are reasonably close to Children's Hospital I would go there. It sounds like your MD office is not doing the tests that are necessary to determine what your child is really suffering from. He could have one problem or three problems that are compounding eachother. I would go to Children's and get an allergy work-up, I would request an x-ray of the lungs. In the meantime, if you think he has allergies - the first thing is to get him on an antihistamine such as Zyrtec, then maybe he could use a nebulizer for albuterol or a steroid short term, sounds like he should also be on antibiotic that he hasn't already been on this year. Once the infection is controlled and the alleriges are under control - he may not need asthma meds. Hope this helps.