Can you help with my mouth as it's too small and my asymmetrical smile? (Photos)

My mouth is tiny. The muscles in my mouth don’t react like most people’s do when I smile. My teeth also sit farther back in my mouth away from my lips so they appear dark when they are actually normal whiteness. The shadow cast on them from my lips makes them appear dark. I recently saw an oral maxillofacial doctor and he said there wasn’t anything he could do for me. Dental veneers or crowns may help but they won’t change the size/shape of my mouth. Please help.