The truth is, I don't know the truth about my fiance.
Do you think that you don't know your fiance well enough?
Sometimes I feel like I don't know who he is.
It's understanable that you feel concerned about the level of intimacy between you and your fiance. You should talk to your fiance about concerns so that you can work on the problems.
I feel like if it gets worse, I'll break up with him.
It's important that you talk to them about what's bothering you. If you leave these things unsaid it could cause a rift in your relationship.