I experienced popping sounds and my doctor told me that it was the baby's joints popping (and yes you can hear it from the outside)and now that he is born, his joints pop and it sounds exactly how it did when he was in the tummy. As for the pain, it sounds normal to me. I also experienced it and the doctor informed me that your hips are getting bigger so it's putting pressure on your back as well as the front of your hips. I would bring it up to your OB though anyway just so he/she is informed of what you are feeling and so they could help ease your mind.
If you want to avoid going in just to be sent home you can always call l&d first. Let them know what happened and they will let you know if they want to see you. Also you can try to call your doctors office to get in touch with the on call. It will give you some peace of mind at least. Good luck and keep us posted :)
If you're still having pains I would call my ob after hours line & see what's the deal. Always better to be safe than sorry