unfortunately there's no way to tell you what's causing the numbness without a physical examination and possibly an x-ray or some other diagnostic imaging. many conditions could cause the symptom you're describing though the likely culprit is a compressed or pinched nerve. even though you only wear low heels the shoes could be at fault. however your best bet is to visit a doctor to get this checked out. it's probably not anything serious but you don't want to permanently damage a nerve by ignoring the situation. hope this helps!
why is the second toe on my left foot partially numb? . i only wear 2-3" heels twice a week for about 3 hours each time. other than that i am usually barefoot. actually i spend most of my time laying down.