Ligaments can be tightened up with Prolotherapy, or surgery where they sew them tighter. They cut out the slack. No amount of PT will help once your ligaments are lax. I did the Prolotherapy but they didn't tell me that I needed PT at the same time and now I am WAY too tight on the right side. I have to do stretches to try to loosed back up.
Every time that your pelvis is out of alignment, it will hurt. There are exercises to get you back in, but if your ligaments are lax, you have to keep having it done. They told me to lay at the edge of the bed and hang the leg over the bed, from the hip down, on the side that is too tight, to loosen mine up. Also, I have to do hip flexor exercises. This again, is to loosen up. You don't want to do any stretches that loosen you any further.
Surf the web for SI exercises and then go to a good Osteopath who can lead you in the right direction. If you choose Prolotherapy, make sure that you do your reseach on the spine doctor doing it. It is big money these days and most insurance won't pay for it.