Please please please go and see a physio who specialises in women's things (I saw one through the public hospital I was attending) - they will give you some tips and tricks on what to avoid and how to do the things you need to do. They might also give you a support belt or tubey thing to wear to keep your pelvis better supported. Don't let it drift as it can get much worse and you don't want to be using a walking frame by the end of your pregnancy!

There's an excellent website called The Pelvic Instability Association with lots of helpful information.