What is this pain from?

A year or so ago I had severe pain in my upper arm/shoulder area. Both arms. I went to the doctor & had a scan that showed nothing was wrong. The pain was unbearable, I could barely use my arms. Some months later the pain went away by itself. It didn't matter as much back then because I wasn't working. Now it has just returned, just over a year later. It gets MUCH worse at night and I can't sleep on my sides...I can barely sleep at all so I am always tired at work. I don't want to pay $50 for a doctor who will say they don't know what's wrong. Does anybody know what may have caused this? I haven't injured myself at all. I'm a 20 year old female.