Hi L.,
Here is my 2 cents. I would absoultely trust yourself, 100%. You are mom and you know your child. The doctor can only tell you his opinion based on what he sees for himself. My daughter is 26 months, and I've thought she has has syptoms of asthma since she was 6 months, our family has a strong history of asthma, my grandmother died at 61 yrs old, because of ther asthma. I have mild asthma myself, and get syptoms when I'm around cigarette smoke, flumes, or have a cold. I have a neulizer that I give myself albuterol treatments with and I have given my daughter treatments with it when I feel that she needs it too. Much like you, I have taken my daughter to the doctor several times, with a cold that is in my opinion worse than normal because of asthma symtoms and the doctor just says its a virus and I'm overly concerned. But I don't think being overly concerned is the problem, but instead the limited time that doctors have to form their opinion. If your sons is responding to the asthma treatment, then I think you should have him tested. Because, for my daughter the pediatrian has told me that she is too young yet to be tested, but if the treatment is working then its working and use it.
The steriods are scary! I would be very cautious in using them. The albuterol is ok and not harmful. But the steriods can have negatives and become less affective. If you are needind steriods on a regular basis then definately a asthma controling medication should be used instead.
I hope that helps.
TRUDI