I'm going to limit myself to a single idea, which I suggest you repeat over and over to yourself like a mantra: If you don't get this area of your life handled, sorted, managed and mastered, you are in for a very unhappy life.
You'll not only make yourself miserable, but crazy as well. From what you've written here, it seems like you're well on the way. You talk about driving past this girl's house to check on the cars parked outside? I don't know if that's immoral per se, but it sure is loony as hell.
You come across in your posts as very young, totally inexperienced (you admit as much), and utterly, absolutely naïve about women and relationships. This is not a crime, but also it's not a state you want to remain in for long.
While you're crushing on and obsessing over this one particular girl, the reality is she is of no significance whatsoever. You think (or rather, you feel) that she is someone extremely important, when in fact she is nobody, irrelevant to the big picture.
The important person here is YOU. You need to focus on improving yourself, bettering yourself, and above all gaining a mature sense of emotional perspective, particularly where sexual emotions are involved. In short, you need to make yourself into the kind of man who doesn't get irrationally obsessed with girls like this.
Now that I've beaten you up, let me say there isn't a man reading your posts who can't sympathize with you, at least a little. Fortunately for some of us, your story serves as a reminder of our distant past. For others, the pain you describe is like an experience out of the movie Groundhog Day, something to be revisited and re-encountered again and again.
The unfortunate reality is that most men never get this area of their lives handled, sorted, managed and mastered. They never really figure out sex. To the average man, sex — and its attendant features, such as attraction, masculinity and femininity, etc. — is always a bit of a mystery, which is why so many men make such humiliating wrecks of their sexual lives.