I have problems with my right shoulder very bad pain,feels heavy ...

I have problems with my right shoulder very bad pain,feels heavy to lift it.I started getting injections 1 1/2 years ago my doctor gave them in my joint area of the shoulder.Now he has a Dr.assistant working there she sees patients because he's backed up I told her I needed a shot she gave it in my muscle top of my arm,said it works just the same as the joint I disagreed said it wears off to fast and I'm afraid it will damage the muscle in my arm.Of course she said no it doesn't hurt it but she's wrong I have had more problems with my arm since she started with injections in that area my muscle hurts so bad its like having a tooth ache you can't touch nothing helps it I have problems lifting my arm.I believe the cortisone medicine doesn't work its way threw the muscle all the way that there is residue left in the muscle tissue.There are other medications that you take and even after you stop taking them they stay in the fatty tissues for 30 days so why is it so hard to believe that these injections do the same thing