NO Not a sin(whatever gave you that silly idea?) Marriage is a cultural construct. sex is necessary for procreation procreation is necessary for the continuation of the species without sex, we become extinct
According to the more rigid patriarchal religions, sex for any reason except to propagate the legal husband's lineage is a sin - even recreational sex within marriage. Hence the rules against contraception and intercourse during menses. But at least the most god-fearin', gun-totin', lock-em-uppin', wall-buildin' Merricuns are hell-bent on punishing women who do have sex without intent to conceive by denying them birth control, health-care and child welfare.
I thought you were a Christian? Haven't read the Bible, yet? Anywho, here's a Christian who says sex before marriage is a sin, and he supports his claims with Bible verses: https://corechristianity.com/resour...that-teach-that-sex-before-marriage-is-a-sin/ This author says that it could go either way: https://www.focusonthefamily.com/faith/three-lies-about-premarital-sex/ And of course, articles that say sex is not a sin: https://cluecho.com/8834/uncategorized/sex-marriage-not-sin/#:~:text=What is written about sex,sins against his own body. So, as we can see, the Bible is not a book that actually explains anything with clarity and that it shows religious folks will indeed interpret the Bible to mean anything they want it to mean and remain fully justified in their beliefs despite the fact others see it very differently. So, feel free to have sex or not, it doesn't matter because you'll always find other brethren who will support your choices, or not.
alternately: Jesus died for our sins so If you think that sex is a sin, and do not wish to make Jesus' sacrifice meaningless: Get out there and sin. Do it now, and do it often.
Jesus doesn't care. He didn't even care when he was alive. He cared about desecrating the temple with commerce; he cared about mistreating the poor and unfortunate; he cared about failures of kindness and forbearance. I don't recall him once mentioning sex in a disapproving manner - in fact, the only reference he made to it was in defence of a woman who "had loved much" and against those who would judge her.
“I find something repulsive about the idea of vicarious redemption. I would not throw my numberless sins onto a scapegoat and expect them to pass from me; we rightly sneer at the barbaric societies that practice this unpleasantness in its literal form. There's no moral value in the vicarious gesture anyway. As Thomas Paine pointed out, you may if you wish take on a another man's debt, or even to take his place in prison. That would be self-sacrificing. But you may not assume his actual crimes as if they were your own; for one thing you did not commit them and might have died rather than do so; for another this impossible action would rob him of individual responsibility. So the whole apparatus of absolution and forgiveness strikes me as positively immoral, while the concept of revealed truth degrades the concept of free intelligence by purportedly relieving us of the hard task of working out the ethical principles for ourselves.” Hitchens Not only meaningless, but immoral, as well.
