what makes u so sure that it is true SIJ pain??? in The body area u mentioned it could be LOW BACK pain from somatic structures in the lumbar spine (discs,facets,muscles)..Perhaps u should recheck the lumbar area, pay caution on the aggravating/relieving factors to pain and then embark on your treatment regime.
P.S. "palpation" tests on the SIJ are by far unreliable, as it has been proved in many studies...U better use "pain provocation" tests which can enlighten u much more!