up at five again

I woke up with shoulder pain at five again, same as yesterday. There's a burning sensation around my entire left shoulder, and a stinging pain at one particular point near the back and top of the shoulder.

Waking up with pain has been fairly frequent since January (that's about two months now!). However, it has changed from waking up at a normal hour, and feeling pain in the shoulder, to waking up really early or in the middle of the night due to the pain.

I had my third physical therapy session yesterday, which may have made things worse in that regard. The therapy was incredibly painful. It was difficult getting to sleep because of the lingering pain last night. I decided not to take any medication for it, just to see if the pain would subside overnight, on its own, but no luck.

After the first PT session, which was somewhat painful, I felt like I slept somewhat better. The second PT session was horribly painful, and I haven't slept well since then.

Usually, after waking, it takes anywhere from ten minutes to several hours till my arm stops aching. I find it very strange that lying down aggravates the condition. I mostly sleep on my back - why does that make things worse than sitting upright all day long?