Need help, will a better mattress help me with my back pain?

I have mind scoliosis and lately i have noticed that some of the bumps on my spine have disapeared (i think they went inward...) anyways, I am sick of always being in pain, my husband wont get us a new mattress because he says the one he has is good for his back, he has degenerative disk (hes 42)...anyways, im sick of sleeping on the couch or the mattress and want a new bed and since we are not rich i have resorted to possibly buying a single bed just for me, but i dont know what kind to get, iam 6 feet tall and 29 years old, and very sick of having such a bad back..please help!!!