Sex feels good for a reason. If it didn't, species would go extinct by generation's end.
Bodily functions tend to feel good for a reason. How long can you subsist on meals of castor oil or that did not have any flavor? Sex isn't vital despite feeling good, it feels good because it is vital.
Everytime someone engages in sex, a pregnancy does not occur. In fact, most don't, and of those that do, a large amount result in miscarriages, also known as spontaneous abortions. Most of those occur with the woman not even knowing she was pregnant.