Obviously, I am not speaking as an authority of the Church, nor on anything that is official Catholic Church teaching. I am simply sharing with you things that I have been thinking about and considering when it comes to this issue you are struggling with. There seems to be more that needs enlightenment surrounding all the realities of the act of intercourse outside of marriage.
However, these things should not weigh down the minds and hearts of people. We have to remain practical, and we have to maintain a healthy respect for the things we may never know about this side of heaven, nor should need to know in full before proceeding with acting on the necessary things of life, especially the vocation to marriage.
I don't want to see good people capable of being good husbands and wives over-thinking, or second-guessing themselves about whom to marry based on past sexual experiences or virginity. There is no doubt that remaining a virgin until marriage is the ideal, and quite attainable for any person of faith - and a virgin has every right to feel strongly about marrying another virgin. After all, if you have saved yourself for marriage because of what it means to maintain virginity and have that to give your spouse on your wedding night, why shouldn't you want someone who has saved themselves as well? But someone who is not a virgin I don't think has that same right to insist on marrying a virgin. That seems hypocritical to me.
In the end, the most important thing is finding a suitable partner to give yourself completely to in marriage because of the vocation to marriage. Our vocation is the most important thing in our adult lives and what God is most interested in for us as adults. There are too many examples of good marriages between two people who were not virgins. Therefore, I guess my advice to you and anyone else who is struggling with this issue of what happens to two people when they have intercourse is to not let it bother you to the point of never seriously considering someone who is not a virgin. In other words, if you set out to date only a person who is a virgin, you are probably doing yourself a disservice toward your vocation, and probably going to pass up really wonderful people who will make excellent spouses and parents.
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This whole thing may very well be just too much of a mystery for any of us to understand to the point of being able to move forward in making decisions in our lives. So it would be best to focus on the person and not the past. I don't deny that there are other issues to consider with someone who has been very sexually promiscuous in their past. I am not talking about those persons. I am talking about persons who have made sexual mistakes in the past and are now committed to chastity. Those persons many times are "gems" that you just do not want to disregard so readily. In fact, I have found that people who are converts of pre-marital sex are often some of the most edifying, holy, grateful people who are well prepared for marriage exactly because they respond to God's grace and believe in what He has done for them.
I believe in God's grace, and that it has the power to transform anyone into a saint, regardless of their past. I hope you know that I understand your position and your struggles, but I pray that you will take this to the Lord in the Blessed Sacrament and give it to Jesus completely, and beg Him to release you from any aspect of this that is not of God so you will have a better pair of eyes to see the potential in any person you meet that may very well make a great spouse for you. Only then will you be a better spouse for that person you hope to marry one day.