Back pain is the absolute worst. However, it is really comforting that there are so many different ways out there to help you get rid of it. My advice would be to seek professional help as soon as possible. It is a good idea to seek professional help instead of trying to fix things yourself.
Thus, it is bigger in size than a coverlet. Quilt. A quilt is a piece of cloth that is intended to provide warmth to the sleeping person. It is not to be slept over like a bed sheet. However, it remains a bed covering during day time and hence the confusion with a bedspread.
A bedspread can be a quilt or a comforter & visa versa, but not always. It is any textile used as the outside layer on a bed (except for a small throw). They typically cover more of the bed than a typical blanket, quilt or comforter. Duvet & duvet cover definitions are fine.