It is the just on the back side, an inch or so from the top of the hip bone.
By the way, I am 6' 0" 175lbs.
The nature of pain is suggestive of nerve pain which can be caused by the nerve supplying sensations to the area getting pressed anywhere along its course. This may be caused by a prolapsed disc in the lower spine causing a pinched nerve.
(See the link for more information on this
http://www.spine-inc.com/glossary/p/prolapsed-disc.html) An orthopedist would be able to confirm or rule this out by clinical examination.
or from the cutaneous branch of the nerve being involved.
You can get medicines for nerve pain like Neurontin prescribed for you or you may get a steroid shot in the area from an orthopedist to help get rid of the pain.