Hello, Such pain is commonly caused due to muscle strain, backpain can also result from problem with sleeping posture, bad mattress or pillows, back injury, etc. Underlying medical conditions like spinal stenosis, degenerative disc disease, herniated disc, fibromyalgia, osteoporosis, OA, RA etc., can cause similar symptoms. Sometimes, backache also results due to rough, prolonged, doggy style sexual intercourse if she has any underlying medical condition that has not been diagnosed. Go for other positions. Get her clinically examined by a GP, get required blood tests, investigations and imaging tests done. In the meantime, avoid doing any heavy work and stay at rest. She can apply pain relieving ointment or apply Volini spray to get rid of pain. She can take acetaminophen, one stat when needed. She will be given conservative treatment and also physical therapy. Take care. Hope I have answered your question. Let me know if I can assist you further. Regards, Dr. Nupur K, General & Family Physician