I Am 19 And Female. For About A Year My

I am 19 and female. For about a year my left shoulder has been very uncomfortable. It's not painful just a lot of discomfort. I can't sleep on my left side and the only relief is when I stretch my shoulder by pulling my left elbow behind my head or rotating my arm. At rest, the discomfort is mild but noticeable and it tightens a lot when I exercise. It's never bruised or swollen. My father had to have rotator cuff surgery a few years ago, if that has an significance. I was wondering if this was tendonitis or if I possibly damaged my rotator cuff?