Over the past 5 months i have been getting intermittent episodes of breathing difficulty , which starts with a feeling of tightness in the chest  which lasts for about 10 - 15 mins acompanied with shortness of breath. Have undergone a number of investigations like blood tests , chest x-ray , PFT etc , but all reports were normal and was asked to use an asthalin inhaler for the same . Have found no relief using the inhaler and still get the simiIar episodes. I do not have a family history of asthma either. For how long should i continue with the inhaler ?