I am a 17 year old female, what could be the cause of a frequent dull ache in my lower back ( worsens when lying down?

There are multiple causes for lower back pain in females. But the most frequents in a young one are bad position & muscle strain.Be sure you’re lifting in the right way( bending your knees), carry not too heavy backpack and if a side sleeper, find a thin pillow to place between the knees.Use warm packs to soothe the area and Naproxen if severe. If it fails: go to Gen.Doctor(scoliosis,disc hernia..