If you bought into a romantic fantasy that requires your spouse to only have sex with you in their entire lifetime but choose to have sex before marriage, you are in a double bind. Because if you break up with this person, you will still never have the thing you really fantasized about (two people only have in sex with each other for their entire lifetime) since you are now not a virgin.

Of course, you will have already gone against your own values by choosing to have sex with before you getting married.

Ah, now there is the real rub isn't it?

It really important that you either stop having sex with until you marry, or find a way to re-think your childhood fantasy and shift your beliefs to include that it really is okay to have sex with the person you expect to spend the rest of your life with. If you have already made this commitment to each other then you are functionally married anyway and just waiting for the legal and church blessing.

The real message here is that whatever your beliefs are, its vitally important that you don't violate your beliefs for the sake of the relationship.  To do that is to sabotage the relationship.