M.K.
look up Symphysis Pubic Dysfunction and see if what you read there is what you are experiencing.
http://www.whattoexpect.com/pregnancy/symptoms-and-soluti...
do you normally have loose or hyper-extending joints? I do and with my second and now third the tailbone and SPD pains are much worse. Have you tried a support belt or belly bra to take some of the pressure off of your pubic bones?