Ischialgia is one diagnostic possibility for the cause of pain in the leg, especially because the pain that you describe is not due to injury or over-exertion. The problem could be located in the lumbar vertebral column where the nervus ischiadicus originates. Pressure on that nerve can cause pain similar to that which you are feeling. Usually spondilotic changes in lumbar vertebrae create pressure on the nerve’s roots.

You can go to your doctor for an examination and request an X-ray of the lumbar vertebral column, or request a referral to an orthopedic specialist. In the meantime, you can ask for more information about the safety of taking analgesics for the pain.