Chest tightness - shortness of breath

I have been on Toprol XL 50 mg for over a year for high blood pressure. At times (off and on) I get a sensation of severe chest tightness - almost like someone has a belt wrapped around my ribs and they are pulling - it makes it hard almost impossible to take a deep breath -- this can last from minutes to HOURS and is driving me insane. At first I thought I had developed adult onset asthma, never suspecting it could be the Toprol - but after going on Flovent for the asthma and an albuterol inhaler for 'rescue' - it has not helped in the least. Has anyone else experienced this? Please I feel like I am going crazy - any response would be greatly appreciated.