Sex is good if done with responability. Jesus never condemned sex. Jew law condemned sex, but also condemn other things that Jesus said were not necesary to condemn.
When you go right to it, there were no anticonceptives in Jesus times. It´s not like he could have sex "Sex is good as long as you use a condom".
There are very effective ways of not getting unwanted pregnancy. Speciallly with a woman you know because it got to do with their days and periods. Even for inconsistent ones there are measures to be taken by body temperature to be sure when are the dates.
It pleases both man and woman and harms nobody, so it is good. "Do untho others what you would like done untho you". Well, that´s more or less what sex is all about
All the consecuences come from irreponsability, not from mere sex.