Note
So the MRI results are in, and Dr says no rotator cuff tears. Some impingement and a little arthritis, with both leading to pressure on the rotator cuff and so muscles are likely tightening to relieve the pressure. PT, cortisone shot, and then if that doesn't solve it then consider surgery to create a little space (but I really don't want to go down this route). Cant do any damage, so do whatever I can tolerate pain wise.
Addendum: Physio isn't totally sure of the diagnosis, given how things are presenting. MRI wasn't with contrast, so small tears could perhaps have been missed. Still going to go ahead with a cortisone shot and PT, and hope it clears up......