Pregnancy does cause some tolerable pain in the bones of the pelvis and spine. If you already have some problem with the symphisis pubis, the pain is sure to get aggravated with advancing pregnancy. Regarding the baby changing his position (which normally occurs after 32nd week) there are many causes for persistent breech presentation - one of them is a contracted pelvis. It is not possible for me to predict what will happen in your case without examing you.