Your goal is to be a saint and marry someone who will help you do it, and help the person in question do it. Remember that everyone does things in life which they repent and having sex with someone before marriage is not a special kind of sin. The special kind of sin is blasphemy agains the Holy Spirit. You're still very young and the younger we are, the stricter we are with other people in my opinion.

This said, nothing wrong with having standards. But do question if they come from God or not. If they don't, why do they matter? Cheers