Breathlessness

I was diagnosed with HCM a few years ago and have had medication that has been fine.A few months ago I had 2 stents inserted as one artery was 70% blocked the other artery is slightly furred.i have been breathless but only on walks if I go up an incline.Since the stents were fitted I am extremely breathless even on a flat walk and have had to use an invalid chair whilst getting around Disney land .I have had every test done since complaining to my doctor about this ie stress test ultra sound etc I was even sent to a lung specialist who did a bunch of tests which all came back fine.I was told to stop my Bisoprolol to see if that could stop the breathlessness which it hasn’t.The last result is an MRI scan to see if that shows anything but I am reluctant as I have been told my heart is working fine as well as my lungs. I am desperate to know what is causing this breathlessness as I am slightly over weight but feel worse after the stents and I had another angiogram to check stents were in place and was told everything’s fine