Lower back pain last 20 days is it normal?

It is totally normal to have lower back pain during pregnancy as your body preparing to carry little one as well as labour. You might want to do proper stretching/exercise for back posture. During sleep to have atleast cushion/pillow as support. If this persistent and you can't endure, you may also use maternity support after few months as well as seeing doctor for cooling gel/cream for back pain.