Tendonitis in shoulder

KarlXII

I have gotten myself a tendonitis in one of my shoulders (in the Supraspinatus), and I am feeling that it is not healing. I have a constant pain there, and it feels worse when I try to lift my arm up to the side. I have had it for three weeks now, and it is quite frustrating because I can`t train any of the muscle groups in the upper body where I must use my arms. I am also worried that it will take several months for it to heal, and that I will lose a lot of my upper body strength during that period because I can`t train this muscle groups.

The only muscles I feel I can train efficiently is my legs and abs, but only with bodyweight exercises.

So I wonder if anyone here have any tips and advices in what I can do to make the tendonitis heal more efficiently?