Shoulder pain. What do i do?

I am having shoulder pain for a while now. I first noticed the pain on my left shoulder while doing overhead presses at the gym. When it came to a point where I couldn't do overhead exercises anymore without pain, I stopped doing them. This went fine and I discontinued going to the gym for about 8 months. I rejoined and expected the shoulder issue to have been fixed since it had gotten so much rest. But when I started doing overhead presses, the pain returned from the 1st day itself. So I avoided overhead shoulder exercises and continued with other exercises. After about 3 months of regular exercise, I started feeling that sharp shoulder pain while doing other exercises as well, like the bicep curl and tricep. Soon it came to a point wherein I couldn't do any exercises that involved my shoulder. The pain was present only on my left shoulder. Since then I've again stopped going to the gym and underwent ultrasound physiotherapy at office for about 10 days. But no use. What do I do?