U need to consult. Might require surgery also.

Are you doing regular back strengthening exercises? If there is a dynamic instability then surgery may be required.

Does the pain stays in lower back region only or it radiates towards lower limbs as well.. Have you ever done any investigations for this pain.. Is there any instability while standing or walking.. There is a possibility of weakness in ligaments supporting the lumbar spine post delivery with a possibility of disc prolapse which might have increasedover the years.

Avoid bending and weight lifting. Reduce your weight. Thanks