When I hold my 13mth old on my hip, the arm im using turns completely purple iwithin 5 minutes when I drive more than 10 mins legs & feet go numb?

Venous congestion. A venous duplex ultrasound of your arms/legs first to assess for DVT. Pregnancy is a hyper coagulable state. Doubt neurologic disorder, but if venous studies are negative and Sxs persist, MRI of lumbosacral spine may yield source of lower extremity numbness.