Ok - can you try something for me?? You will need 2 people whom you trust!

1. Lie down on the floor. Bend both knees up with feet on the floor together in the middle
2. Open up your knees and get person 1 to hold your knees. The best way to do this is to put their right elbow on the inside of your left knee (they are facing you), their right hand/palm on the inside of your right knee. Their left elbow will do the same on the inside right knee and the left hand/palm on the inside left knee.
3. Person 1 MUST NOT PUSH. You will try to bring your knees together and Person 1 will only resist the movement to stop your knees moving. Note the pain and strength. DO NOT HURT YOURSELF - go gently - you can repeat it gradually harder later if you need to!
4. Person 2 will now come in and try to push your ASIS's together. They are the pointy hip bones that face forwards and stick out in anorexic models. Try to push from the outside of these bones to compress your pelvis.
5. While person 2 holds this pressure, repeat the test of resisted knees together.

If you find your strength and/or pain has improved, you will have tested positive for a pelvic dysfunction. You will need to find someone skilled at Wikipedia reference-linkSIJ treatment or pubic symphysis treatment. Osteopathic treatment often can deal with this but you will need a skilled physiotherapist to help you with the exercises.

Let me know what the above test is like. BTW, you can push your pelvis together if you like and just squeeze your legs together against a socerball or better still a basketball or something bigger between your knees (sounds bad huh!?!)

Good luck!