A mattress pad adds a thin layer of improved protection and comfort to your mattress. It slides onto your bed like a fitted sheet and add extra cushion and support, as well as protection for the mattress itself.
Adding layers of soft bedding to your mattress can improve the overall comfort of your mattress. This may include a spare duvet, comforter, or blanket placed directly on top of the mattress, which should help alleviate some of the discomfort.
If your mattress is sagging between the slats of your bed frame, you can place a layer of plywood underneath the mattress. Putting a thin layer of plywood on top will help to firm up the bottom of the mattress.