Lower back and back pain

I have had lower back pain even when walking just a little since I was a young lady.

My back aches when I work too hard or stand after giving birth.

I walk every day because it's good for my back.

But I wonder if it's putting more strain on my lower back.

If you rest well, the pain is manageable, but if you walk or stand a lot, you experience such severe pain that you can't straighten your back.

Are there any exercises that are good for the waist?