I just complained to my GP enough about being short of breath, and he suspected asthma...but wasn't quite sure, as my peak flows always look good in the office. So he sent me to the allergist, they did some more comprehensive testing, and finally diagnosed me.
I had recurrent chest infections which wouldn't go away with treatment, then I was put on becotide and ventolin inhalers. Eventually got sent up to the specialist as was badly controlled.