This is my 2nd pregnancy and I experienced the same thing at around 27wks. I can't remember if it was as bad last time but it is quite normal, just ligaments and things stretching. I found it most painful at night when I wanted to turn in bed, and also felt like my hip/leg joints were sore.
Something I recently found out -for everyones info is that you can get varicose veins, swelling and all that kind of stuff in your virginal area. I got a bit worried when I noticed in the shower one "lip" of the vagina was very swelled up on a regular basis - not really uncomfortable or painful though, so I asked the midwife about it. It never happened in the last pregnancy but it's apparently due to pressure from the baby which varies depending on which position they are in.
Kristina, Mum of James 3yrs & Matilda 14 months