I have to hand quilt at the dining room table, with a chair on either side of me, so the chairs and the table in front of me take all the weight of the quilt. When I tried quilting on the couch, my arm supporting the quilt would get terribly sore because of the weight. You didn't specify which part of your arm is hurting.
I also use the Thimblelady thimble, but the plastic version, and the folding method she teaches. There was too much wrist movement and finger bending for me with the traditional quilting stitch.