As others have mentioned, you need to speak with your SO. The point of dating is marriage, and marriage is a total, exclusive gift of yourself to the other. If you can’t share all your beliefs and thoughts, then you’re already evading the ‘totality’ of the (possible) future sacrament.
Also, the purpose of marriage is children. And it will be a great kindness to your children to provide them with a solid, Catholic father. To be married in the Church, your SO would have to agree to raise his children in the Church (so he can’t interfere with their sacraments or attending Mass). But your children have the risk of growing up greatly confused. The father is the spiritual head of the family. So a father who shuns that role will give his children the implicit understanding that religion is irrelevant and unimportant. Interestingly, this negatively impacts the children far more than if the mother does not attend church.
See: http://www.battlefortruth.org/ArticlesDetail.asp?id=174<br />The study reported:
“If both father and mother attend regularly, 33 percent of their children will end up as regular churchgoers, and 41 percent will end up attending irregularly. Only a quarter of their children will end up not practicing at all.
If the father is irregular and mother regular, only 3 percent of the children will subsequently become regulars themselves, while a further 59 percent will become irregulars. Thirty-eight percent will be lost.
If the father is non-practicing and mother regular, only 2 percent of children will become regular worshippers, and 37 percent will attend irregularly. Over 60 percent of their children will be lost completely to the church!” (emphasis added)
Furthermore, it will put added pressure on you to persevere in the faith. God created man and woman as helpmates to each other. Marriage is a vocation, which means, if you chose it, it would be your path to heaven if you were faithful in it. A husband who does not believe in eternity or follow the teachings of the Church will not be on guard for your soul. You will not be helping each other get to heaven. At best, you will be trying to help him with the real possibility that he will persist in error.
Which brings me to the final point: Would it distress you at the possibility your husband might lose his soul? “139 In marriages with disparity of cult the Catholic spouse has a particular task: “For the unbelieving husband is consecrated through his wife, and the unbelieving wife is consecrated through her husband.”140 It is a great joy for the Christian spouse and for the Church if this “consecration” should lead to the free conversion of the other spouse to the Christian faith.141 Sincere married love, the humble and patient practice of the family virtues, and perseverance in prayer can prepare the non-believing spouse to accept the grace of conversion.” http://www.vatican.va/archive/ccc_css/archive/catechism/p2s2c3a7.htm
We are called to follow Christ and abandon mother, father, brother. His presence might even constitute a temption for you to lapse in the practice of your faith (thereby endangering both your souls.) If he resisted you and died unbaptized, you might not see him in eternity. It would be very noble for you to spend your life trying to convert him and to save his soul. But it would be very hard. You would need a constant, solid support group.
For my part, I dated my Fiance because he was a solid Catholic. He grew up non-religious and converted a few years ago. If your SO is intellectually-minded, he might like Edward Feser’s “The Last Superstition” (the book that converted my FI). It lays out the Catholic worldview so rationally. I fear that you might have trouble because the liberal, atheistic worldview is so radically different from an authentically Catholic worldview. And don’t forget to pray about it!! Blessings 🙂