Hi,
You may well have late onset Asthma; it is not uncommon. Disturbed sleep due to cough is very telling.The spirometry will be very informative, but reversibility also needs to be performed. This is where (as you may know) your FEV and FEV1 are tested before inhaling a bronchdilator and again afterwards. There needs to be a specific difference in the two readings for a diagnosis of Asthma to be made. Ideally, spirometry should be performed in a lung function lab. It also sounds as though you need a short course of steroids to dampen down your wheeze and reduce the swelling in your large airways, but only after your spirometry. I would suggest also that you should have your sputum checked for eosinophils.
I hope that you feel better soon.