There would still have been sex and procreation prior to the fall, it just would not have involved sin. What that would have looked like we have no sure guide and no way to tell for sure--and we should really be careful even talking about it since the mere discussion may lead some to sin.
If not for sin the sex organs would be as much under the control of our will and our reason as are the rest of our bodily functions. In what is my favorite passage in the book, Augustine gives a number of extreme examples of such control:
We know, too, that some men are differently constituted from others, and have some rare and remarkable faculty of doing with their body what other men can by no effort do, and, indeed, scarcely believe when they hear of others doing. There are persons who can move their ears, either one at a time, or both together. There are some who, without moving the head, can bring the hair down upon the forehead, and move the whole scalp backwards and forwards at pleasure. Some, by lightly pressing their stomach, bring up an incredible quantity and variety of things they have swallowed, and produce whatever they please, quite whole, as if out of a bag. Some so accurately mimic the voices of birds and beasts and other men, that, unless they are seen, the difference cannot be told. Some have such command of their bowels, that they can break wind continuously at pleasure, so as to produce the effect of singing. I myself have known a man who was accustomed to sweat whenever he wished. It is well known that some weep when they please, and shed a flood of tears. But far more incredible is that which some of our brethren saw quite recently. There was a presbyter called Restitutus, in the parish of the Calamensian758 Church, who, as often as he pleased (and he was asked to do this by those who desired to witness so remarkable a phenomenon), on some one imitating the wailings of mourners, became so insensible, and lay in a state so like death, that not only had he no feeling when they pinched and pricked him, but even when fire was applied to him, and he was burned by it, he had no sense of pain except afterwards from the wound. And that his body remained motionless, not by reason of his self-command, but because he was insensible, was proved by the fact that he breathed no more than a dead man; and yet he said that, when any one spoke with more than ordinary distinctness, he heard the voice, but as if it were a long way off.Chapter 25:
We all long for eternal life, yet none of us will have it because of sin. As a result, in this life we can never be truly happy. Our sense of what should be never lines up with what actually is, and so discontent runs through all that we do, think, and say.