Have you been sleeping with a body pillow? If not this might help as I started aching a while ago and have since bought a body pillow which lies on both sides of me (handy for when I roll over) and have found it an absolute godsend. It kind of makes me lie in the middle of a nest so I don't get any pressure points.

However I now have Pelvic Instability which is what it might be, so you should go and see a physio or osteo for diagnosis and treatment. They might give you a support belt to wear. I think there is a belly belly article on pelvic instability and if you google pelvic instability a site comes up with all sorts of handy hints on how to avoid aggravating it.

HTH!!