What's Wrong With My Teeth?

I can see my bottom teeth go all the way down. I barely have any gum down there. Also, I just lost my bottom canines and they grew in pretty sharp, thin, and long. I'm not saying they look like vampire fangs but they're pretty close. I lost the molar right next to my bottom canine and it took forever to grow in. When it finally did, it grew in like a regular molar but then it sharpens and curves inward. It sort of looks like another canine with a base. I can brush my teeth for 5 minutes straight and they are still yellow. I don't drink coffee or smoke. What's up?