Hello. My Bottom 4 Teeth And Especially My Center 2

Hello. My bottom 4 teeth and especially my center 2 bottom teeth (the one on the left has alot of white showing at the bottom when I lower my lower lip. Could you kindly advise what hits is. There is white stuff forming on my teeth but only on the edges and on that one left tooth I just mentioned. None other of my teeth have any white. These 4 lower teeth are also especially sensitive. I would grealty appreciate any advice as to what is plaguing me.