i know how you feel and many have similar problems.
after giving birth the pelvis sometimes does not go back to its proper position and this ´misalignments´cause muscles to tense which in turn sooner or later cause pain.
yes you may have a condition which is called sciatica and this is the case in most lower back pains although other factors may be present like high acis in the body or stones in organs etc. there is no back pain without misalignments and the root cause is to be found there.
check the exercises etc in my website and try them (any questions ? just email me then) http://www.dorn-method.com
i also have a forum and Blog here.
blessings
thomas