A feast for the eyes!

I have been with him for 3yrs he is the only realy boyfriend i ever had i love him so much we are engaged to be married i planned my wedding 3yrs ago i want to have kids and all of that but recently i've been wondering is he realy the one?no chemistry between us i mean he doesn't blow my mind away when we kiss,i don't feel connected to him he's a great guy he loves me i don't realy know how to fix this but I don't want to leave him either. I do love him I just don't have that loving butterfly feeling and it is something I know should be there in any relationship! we don't cuddle or have intimacy very often we can be togethere in one room and hardly kiss or even touch sometimes i feel that we are not attracted to each other and the chemistry is not there i never day dream of his kiss or desire him .Doing it is good but i don't feel the passion In the long run am scared what if we get married and it never works? I don't know what to do either..... but I don't plan on leaving i love him so much but i don't realy feel love i don't feel intimacy with him we are not twins as they say many people think we are meant for each other but i know deep inside me something is missing please advice....