My rear sides ache and only just started last eve. seems progressively worse. started on left to right now both ache below hip?

I assume there has been no injury or strain, recent excessive exercises, repetitive stair climbing or prolonged sitting on hard objects to account for the pain. Bilateral.ischial bursitis is a possibility. If the pain is radiating down to the back of your thighs, inflammation of both sciatic nerves may be the problem. Rest,take anti-inflammatorys like ibuprofen. ?See your MD or an orthopedic MD