@REI-MichelleW got you started with some good ideas. As a sometimes-in-a-hammock-but-always-looking-for-more-room-in-my-sleeping-bag type sleeper, I've got some recommendations that may help narrow the search:
Big Agnes sleeping bags are some of the widest sleeping bags on the market. They also come with a sleeve that you can slide your sleeping pad into that helps you stay on the pad while you are sleeping. The two Nemo sleeping bags are shaped in a way to give you the ability to move around and flex while you are sleeping. The REI Co-op Igneo sleeping bag comes in a wide width (which I own) that gives you extra room.
All of these sleeping bags are compressible and light enough for backpacking. I hope this helps, let us know if you have any other questions!