Suggest Treatment For Severe Shoulder And Outer Bicep Pain For Two Months, Worsening In The Last Month

I have severe pain in my shoulder and outer bicep for about 2 months now and within the last month the pain has become a lot worse and constant. When I move my arm suddenly or in the wrong way it feels like someone hit my bicep with a baseball bat at full force. I know I didn t break or fracture any bones and the only thing I can think of that caused this injury was doing pull ups or hitting posts in the ground with a sledgehammer, but I did not feel anything at the time, the pain gradually came. I got an ultrasound done and it came back with no results. I believe an ultrasound detects ligaments, tendons, muscles, soft tissues and tears, so if my injury is not related to bone or soft tissue damage, what else could be causing this severe pain? The pain scale 1-10 when I move my arm wrong is about an 8 and the constant pain is about a 5. I don t have any known health problems and I m healthy.