I had 'growing pains' from 9 weeks that lasted until around 20 weeks, then the braxton hicks kicked in. My pains were very similar to what you have mentioned, mild cramps in my hips lower tummy and back.
I think if you have been active on a particular day, then you might feel some mild pains, but try not to freak out when this happens. Sit/lie down and relax until you're feeling better again.
If at any time the pains become too much for you, you can take some panadol, or see a dr to be sure.