21 week pregnant and whats up with my leg?

part of my outer thigh on my left leg is numb and every so often it feels frozen (numb perminatly tho) and it gets lots of painfull tingles. i want to know whats up with it, i am 21 weeks pregnant with my 2nd baby the same thing happend in my 1st pregnancy but it left that part of my leg perminatly numb i can stab it with pin and i dont feel it whats going on has anyone else experianced this and does anyone know what it is or causing it casue no one will tell me at docs