How Far Down Do Teeth Go into Gums and Jaw? (photo)

It might be hard to tell in these pictures but my teeth seem to be getting bigger due to gums receding really bad. My question is how far exactly do your teeth go down? I'm scared and feel like my teeth are about to fall out of my mouth and I'm extremely worried how much longer until they actually fall out? I can't make it into the dentist for another week, and will I even have these teeth by then? I might just be very paranoid but main ones I'm concerned about I have marked with a pink circle.