Have you had a biomechanics expert look at your running form? (not a self-appointed 'expert' with a camera, but a medical pro - Roehampton Uni will do it for around £150, for example). If you're over-straightening your leg when landing (most runners 'overstride' btw) that will put all kinds of pressure on your glutes, hams, back and calves.

Remember that your feet should strike the ground at least 180 times a minute. Any less than this and your feet will be on the ground for an unhealthy amount of time (studies have shown 180 is a healthy minimum - elite runners will strike at 190+ Try running with a metronome, pretending the ground is hot coals or egg shells)

Also - are you a healthy weight? Your feet will hit the ground several thousand times during a run, so every extra pound can have an effect.

BTW - I'm not a physio, just an avid runner with 10 yrs experience.