Hi, This seems to be prolonged muscle weakness causing you pain and wrong sleeping posture or sleeping on a spring mattress might increase the pain specially in the morning which settles down after sitting. but since its been a year the condition is developing into chronic pain and if not treated might lead to worsening and can cause various back conditions. you should get yourself consulted and start with physiotherapy as it will prevent you from further injury.
Next Steps
get consultation to understand the exact root cause.
Health Tips
avoid sofa sitting, slouch sitting, while sleeping place a pillow below your knees. apply hot pack in the morning and before sleeping in the night.