My doctor thought rotator-cuff but it's more complicated than that. Bursitis, or frozen shoulder they reckon. I've dealt with it since October 2019 and get a massive pain in my upper shoulder/outer bicep area when the shoulder rotates forward i.e. when my arm goes backward or up. Hand goes numb etc. The pain is severe and renders the arm useless for 10-30 seconds depending on the severity of the pain, which depends on the extent of the movement.
It sounds like you have similar.
I have had a cortisone injection into the top of my shoulder (ultrasound-guided) and that was supposed to drop the pain level so I could do the rehab but it hasn't really. Not keen for another one though, or an operation.
The range of movement is coming back slowly, through my exercise plan which I do daily, and I hope by the end of the year it will be fixed. The pain is the last thing that will go.
Good luck with yours, it's a shot thing to deal with.
Hmmm, I think yours sounds worse than mine as I don't get the numbness and the pain is only severe if i force a particular movement.
I'm not keen on an operation either and hoping (although it's been 3 years) it will recover on it's own. Stick with the exercises, hopefully you'll be sorted soon enough.
You heard that saying...pain in the ass...Well, mine is arm. Lol.
I hope we both get better quickly and can get back to our usual awesome selves. soon.