Welcome to the old, decrepit and decaying club.
Try bending your elbows and pulling your arms back until you can feel the weight of the gun and your arms transfer to your shoulders.
Sometimes when things hurt a lot, pulling your arms in further, until your upper arms are against, and being supported by your sides, helps, too.
Also try different elbow angles relative the amount of pain.
I find that aiming the elbows down instead of out helps.
Using elastic wraps helps some more.
I do feel your pain.
Lock the doors, they're coming in the windows.