I really like this game a lot, but there are some problems with it the plot namely involving Jamie / Shauna.
The primary storyline doesn't change when it really should.
In the beginning of the game, you have the option to:
A) Tell Shauna you are not interested in her.
B) Tell Shauna you are interested in her, but will not cheat on Jamie.
C) Tell Shanau you are interested in her, and cheat on Jamie with her, however once a cheater always a cheater if you go down this path you are probably going to fuck anything you can.
This should be a MAJOR branching point of the game, but it all goes as if it is on path B no matter what choices you make.
Path A: "The Faithful Romantic" By telling Shauna you are not interested in her this should potentially remove all romantic involvements with her. The game gives the illusion of being able to "steer away" from her, but you can not. This route should be for the classical 1 man 1 woman romance avoiding cheating.
Path B: "Cuckquean Story". Your girlfriend actively encourages you to fuck anyone you want and even add a 2nd girlfriend Shauna.
Path C: "Cheaters story"... Try to keep Jamie in the dark as long as possible about the other women you are sleeping with. Fear for her finding out about all of your cheating. Possibly break up with her, or get caught or some other fun drama like her finding some new dick of her own since you are obviously not faithful.