This started two years ago, when i was pregnant with my fourth child, in the colder months i wear my ugg boots a lot and when i take them off my big toes and tips of all the others tips are white?

Look up Raynaud's phenomena. Feet cold? and turn white same with hands?

This could be a circulatory problem as Dr Grim as indicated. Because all your toes are involved I to think of possible circularly diagnosis. However, your feet do flatten with pregnancy due to elastin fibers being present in the Spring Ligament or talo - - navicular ligament. Thus can make your boots feel smaller