About a week ago I got very sharp stabbing pains in my left back just above the pelvis while out running. Only lasted about 30 secs but very painful. It happened again the next day while running and later while sitting. A couple of days without problems but since then the pain has been recurring frequently while runnng, sitting, standing even lying in bed, though less severe then. The stabs of pain sometimes go on longer now, though probably no more than a minute or two - just feels longer. Anyone any idea what is going on and how to prevent it?