Hi Joyce,
It is hard to believe that you are already 21 weeks! You are over halfway there. I am not great when it comes to describing exercises in writing. I need pictures, but here goes..... You can stretch each hip in a seated position. Start with both legs out in front of you. Bend one leg into your body and cross the foot over your other thigh. Gently pull the knee in and rotate your torso into the direction of the hip that you are stretching. Repeat with the other leg. Hope this helps. Please let me know if it makes sense too!
Sheila