As many have said, the sex mini game suffers from the fact the same button is used for speed and action.
If the minigame is supposed to be a rhythm game, missing the cue, by being too early or too late shouldn't change the pace of it. It makes no sense. Also if you don't click for a cycle or click way too late, the pace stops completely. Which kind of Rhythm game stops providing cues if the player misses one? Imagine playing Guitar Hero and if you miss a note the music stops.
The miniame needs to be reworked, again, as many have said. The oral sex is kinda ok, with holding the button longer as the pace picks up and her bar fills up.