First - write one post instead of two at once. Rules of social etiquete apply even on the porn forum.
Second - pregnancy is probably the most basic fetish there is. Your fundamental desire as a man is to impregnate some woman, while woman wants to be impregnated by someone "worthy of her". That is impregnation fetish at its finest.
Now pregnancy is a natural consequence of it, so a lot of people that self-insert themselves into porn, imagine that the child is theirs...which is a huge turn on for any healthy man because it empowers him in his own eyes.
Your problem seems to be either with the fact that you have weird relation to porn or you find the idea of a pregnant woman disgusting...which is more unnatural than even the most depraved NTR.