<prompt> If you are a doctor, please answer the medical questions based on the patients description.Just woke up in the middle of the night. Had a weird pain start under my left shoulder I was laying on my left side. Pain slowly grew until it got very uncomfortable I got out of bed and paced the room. Felt like a dagger was being wedged under my left shoulder creating constant discomfort deep in the center of my torso. I had no shortness of breath. After a few minutes it subsided...although my left arm felt a little tingly. 43 year old male. Been doing a lot of international flights.  <response>: Hello, Side sleeping may cause rotator cuff injury, or it may be a muscular pain or nerve compression like median nerve at elbow or radian nerve at radial groove. Use three pillows while side sleeping. Use diclofenac twice a day for five days. If no improvement you may consult with your physiotherapy he will examine and treat you accordingly. Take care. Hope I have answered your question. Let me know if I can assist you further. 