Oh Grow Up!
Marriage
There were certainly pre-marital relations and extra-marital relations. The Church moralists condemned such things, of course, but could do little about it.
Marriage was a civil ceremony in the Middle Ages. Toward the end of the MA, more and more marriages were being "blessed" by a priest, but marriage as a sacrament was still largely ignored.
The first step in marriage was negotiations. The more property involved, the more important were these negotiations.
The other family had to be checked out. The women played a key role in this, knowing who was of good reputation and who wasn't. The men checked out the finances, but the women checked out the reputation.
The son or daughter would be kept apprised of this and their input was accepted and expected. Again, the more property and status were involved, the less the individual prospect's preferences counted, as a general rule. But there were lots of exceptions.
Once an agreement was reached, then came the betrothal. This was a formal promise between the two parties that marriage would follow. There might well be a formal contract and the betrothal was also the occasion for formal agreement to that as well.
The two families were now in agreement, but the community had to assent. This was done in the form of reading the banns, a public proclamation done on the steps of the parish church. An interval followed (three weeks, in rural England) to give the community an opportunity to raise objections to the match.
With no objections heard, the day for the marriage came. Both families trooped off to the church, and the exact form of this was highly localized, with songs and rituals attached.
At the church, the ceremony was performed outside or at least outside the sacred precincts. This was a civil ceremony, though a priest was typically present. Now the dower and dowry were announced publicly to the gathered audience, doubtless with considerable comment. The bride and groom stated public vows. Here are the words from 15th c England:
I take thee W to my wedded wife, to have and to hold, from this day forward, for better for worse, for richer for poorer, in sickness and in health, till death us do part, if holy church it will ordain, and thereto I plight thee my troth.
The woman's vow is similar yet different:
I take thee M to my wedded husband, to have and to hold, from this day forward, for better for worse, for richer for poorer, in sickness and in health, to be bonere and boxom, in bed and at board, till death us do part, if holy church it will ordain, and thereto I plight thee my troth.
(bonere and boxom means something like obedient and cheerful, or good-natured and hearty)
After these words the rings were blessed and exchanged. The priest hoped the couple would then enter the church for the Church's sacrament of marriage, but few peasants or other ordinary folk did this.