I'm there with ya... kinda. I'm only 6 weeks along. I have hip displacia (unk spelling). It's kinda the same thing big pure bread dogs get like rotties and boxers. (note- I am not a pure bread! :) ) My hip bones are built tilt forward and rotated to the left. It hurts to walk before I even ever though of having a baby. Have you had your hips checked out? I have had this since the day I was born. They noticed it when I was learning to walk and found out I am pigeon toed. I look and walk normal but you would have never known without a full back/hip x-ray I got years back.
Rub lots and lots of lotion. Try pelvic tilts, too. You get on your hands and knees. Round your back (like a cat when they get freaked out) and then straighten your back. Also, if you have an exercise ball, you can GENTLY bounce on it.
It is not just your ligaments stretching. Your hips are actually ROTATING into a new position. They rotate down so that the baby can come through your hips, into the birth canal, and into the world.