Back problems

I have arthritis and scoliosis (if you don't know what scoliosis is it causes your spine to be curved) I was diagnosed with these things when I was around 13 maybe younger. Anyways I had a baby two years ago and after I had him it's like my arthritis pain and the little back pain that I had went away. Well two years later and the pain is coming back with full force! My back is hurting SO much I really don't know what to do, it kills me to bend over and hurts so much when I have to carry my son around (he's 36 pounds). I also have a fairly firm mattress that isn't helping the problem, but I'm currently too broke to just go out and get a new bed. Also the arthritis has been bothering one of my legs super bad in the morning, and half the day. When I get up I literally have to limp because of it. I'm only 17 years old and it sucks so bad to have these problems. If anybody has any suggestions on what I can do to help my back pain that's not crazy expensive please let me know! I don't have insurance right now or I would go to the doctor.