How did you get the true ending
Just choose the following options,
John would want you to let it go (use the arrow keys to choose the option, as the mouse will fight you here)
Explain fully
Start making dinner
Have sex! (the mouse is REALLY insistent here, just go with it, it is the best option XD)
Ignore other and find John (all the text options here are actually different to what she really thinks, what you see when you highlight the options is her real thoughts)
Take John's idea
Have some fun (H-Scene 1)
Be quietly supportive (choosing the other is a horrendously bad choice)
Kill her (hover your cursor over options until you see once change to Don't kill her yet)
End the conversation and tell John all about it
Explain the thoughts that went into the notebook (NECESSARY FOR TRUE ENDING)
Ask John about it (choosing ignore just makes her worse then reloops the option)
...trust him. (make certain you choose the option without the capital letter! If you chose to explain notebook earlier you know why this is important)
Then enjoy the final H-Scene and ending!