Possible rotator cuff tendinitis

I am sorry to hear about the problems you are having with not just your shoulders but all the other problems re arthiritis.  48 is so young to have started, my best friend now living in LA has had it since she was in her 20s and she is 73 now.  She has both forms of arthiritis and has had 5 hip replacments.

I too have similar shoulder problems like you, in my right shoulder.  About 3 years ago I slipped and fell on a wet floor and severely bruised my right side of the body.  I was travelling home to Fiji a week later.  At the time I didnt feel too much pain, with the exception of the bruises.  However, in Januiary last year I started to experience a lot of pain in my right shoulder - like you, I couldnt do many things, with the arm, had a lot of pain on the upper arm which caused me a lot of sleepless nights. 

My GP first sent me for X-rays which just picked up on wear and tear.  He referred me to see an orthopaedic consultant - privately - who after getting me to do certain movements diagnosed it as rotator cuff problems and impingement issues.  I was offered a guided steroid injection - ultrasound - and this is when he found I had a 25mm tear in my supraspinatus muscle.  He recommended physiotherapy which I have had and failing that perhaps a keyhole surgery.  I decided against surgery, given my age, and opted for physio/ortho exercises.  My physio taught me a number of exercises to strengthen and stretch the remaining muscles which I must do daily, for the rest of my life. 

I still have pain but I must say the physio exercises have helped enormously and still does.

I hope, after ultrasound, you get a proper diagnosis.  Best of luck.