@flib Many people find it difficult to breathe in a mask, especially with any kind of diminished lung function. It is not your imagination as one man here tried to tell another - the fabric inhibits the movement of air - exactly as it is intended to do. I certainly prefer to be without one, but am able to just push through it. My masks are made of two layers of sturdy quilting cotton, pleated in front, with elastic around the head. They are approximately the same in permeability as the surgical masks (not N95 respirator mask.)
N95 masks are another matter - I truly do struggle to breathe through those, which severely limits my pleasure in working in the garden, where I wear it when digging in or scratching on the soil due to my lung issues. My daughter, an ER nurse, suggested wearing your mask as much as you can stand, even around the house, to build up your ability to breathe through it - that is what they counsel new employees who have trouble tolerating it.
I hope you find a solution that works for you, as I believe many of us will be wearing masks in public for a good while.
Sue

I have the same problem. I find it helps a little if I breathe through my mouth. Also, If I find myself really struggling while exerting myself, I stop and concentrate on slow deep breaths until I feel a little better.