there is a condition called sacroiliac joint dysfunction that can cause pain in that region. i have suffered from it for both my pregnancies and i have to wear a belt plus go weekly to physio and hydrotherapy to try reduce the pain. not sure if the symptons are completely what you are experiencing, but google it and have a look. unfortunelty they will not be able to get rid of it but doing things increase your muscles strength and eliminating or reducing the triggers that cause it.