I Have Been Having Swelling In Both Of My Arms

I have been having swelling in both of my arms inside the elbow crease. When I took pics of them for my doctor they showed up with a rash on them, but I don't see the rash myself. I've been getting woken up because my arms feel like they are breaking in the middle of the night. I have fibromyalgia, but have never had this problem in my arms. I almost always have some sort of swelling in my knees tho and they have both been replaced.