Left vs. Right

I noticed something this weekend of concern. I’m lopsided.
I was looking in the mirror and got a good glimpse of my pectoral muscles. The one on my left looks pretty good, dare I say sexy, but on the right it looks… flaccid. I’m assuming that this is because of my shoulder injury. I must be favoring my left arm leaving my right muscles to atrophy.
The solution I suppose is to start forcing myself to use my right arm more. Which shouldn’t be a problem since I am right-handed. It should be my natural behavior. Except evidence is proving otherwise.
I want to concentrate on my running form. I might not be swinging my right arm the same amount as the left. That might also be an explanation.