Why does my hip hurt all the time

I have had hip pain on my left side. I have gone to many doctor appointments to find answers but the doctors keep telling me there is nothing wrong with my hip. Walking,sitting, laying down, lifting and bruising around my hip bone but goes away for a couple hours after resting then starts again. I plan to go to an orthopedic to get answers as to what causing my hip to hurt all the time. The doctors said my hip bone is fine but could it be the muscles around my hip.