it's normal. many woman have back pain problem after giving birth.
since u just gave birth, simple execise will help. As the fluid in the joins of the bone decrease later, u feel better.
I do simple exercise to strengthen my muscle and keep its reflexibility. Once I stop exercise and got lots of stress at work, my back pain come back again.
Avoid high heel shoes in the first few months.
Do body massage.
there are some chinese food or soup will help, but personally I don't know how to cook them. U can try to ask other mom for advice.
when u take care of bb in the first yr, be careful when breast feeding, lifting and carrying him. use proper position to avoid further damage to your back.