Complex sentence: This one time encounter resulting in brief sex (though she asks him to stop midway he continues on) makes the drifter become increasingly obsessed with her, later Jessie discovers she is pregnant and not knowing for sure who the father is.
Split into simpler sentences: This one time encounter resulting in brief sex, though she asks him to stop midway he continues on. Later Jessie discovers she is pregnant, not knowing for sure who the father is.