I am 18 and married we are trying to have a baby and we noticed one boob is bigger then the other and its never been that way what could it be?

Probably OK. If you are attempting pregnancy, you should be seeing a gyn anyway, but i bet you that this is just a side to side difference you have just never noticed. If you were to take 2 pictures of your anatomical body, cut the pictures in 1/2 and paste right to right and left to left, you would not recognize yourself in either.