What Causes Shoulder Pain While Suffering From Shoulder Impingement?

Hello. I have been diagnosed with shoulder impingement, and have undergone physical therapy for a month or so, and continuing on my own at home. My problem is improving, as my shoulder and arm muscles are stronger. My biggest issue is I have pain at night while sleeping, to the point of it waking me up. My doctor does not seem to understand my question. My question is, should I still have that same pain after some treatment? The pain is in my shoulder, my elbow, and my forearm. My hand feels like it is swollen, yet it does not appear to be. I take Naproxen often to help with the pain, not sure it helps. I m wondering if the pain is coming from another source. The strange part is that while I am active, I usually do not have an issue, it is the night time pain that is really troubling. Thank you, Dan