Numb legs

Katie🐠 • Pro-choice. 6-24-14
I'm currently 37w and recently I've noticed if I sit down  longer than 10 minutes my legs start to hurt and go numb and tingly like they would "fall asleep" it starts by my upper thigh. Does anyone else have this pain or what it could be caused by ? I've tried walking around a lot more but I get out of breath.