"Should I talk to my fiancé(e) about [this] before the wedding?"

Why is this question ever asked? It is non-rhetorical. Does anyone genuinely expect the answer to ever be anything but "YES"? Consider:

No, you should tell them after you have paid for a costly, intricate ceremony, which is  now stripped of its meaning as a celebration of unions, made hollow by your doubts.

No, you should tell them after you have both entered a legally binding contract that  requires a second lengthy, humiliatingly intimate legal process to null, after which each of you will almost certainly end up loathing the other.

No, you should tell them after the expectations of your relationship have been raised well above its broken reality by everyone you know and love.

No, you should tell them after their expectations of your relationship have been raised well above its broken reality, because after all, they are marrying you.