diastolic dysfunction effects and treatmetn

I sometimes feel like I can hardly move after a 45 minute walk, even though I've been a runner/walker all my life. Also - many mornings, it is so much work to expand my diaphragm just to get a good breath. This lasts for 1 - 3 hours. Sometimes I will use an Albuterol inhaler though I blow my usual normal 325-350 on my peak flow meter (occasional, mild asthma). I am being treated w/Jardiance (10 mg) for heart and also do a Repatha injection once every 14 days. Mu sister, former dialysis nurse, says it's my heart that is causing the exhaustion after exercise - that I'm simply not getting enough blood flowing and that's causing the exhaustion. The exhaustion is not sleepiness - it's an "I can't move exhaustion."
Is my sister's dx spot on? Is the left ventricle simply not sending enough blood over to the right chamber and thus to all my muscles? Same w/ many mornings? I'm quite certain it's not asthma. Looking for info from others. Do you experience this? Is using an inhaler bad when it's not asthma? (I know - I should ask my doc about this - and I will when I see her in a couple weeks but wanted to know what others experience 1st. -