In most cases, sweet guys don't get jack. Why, you ask?
They're boring, predictable, and not fun.
What fun is it for the girl when she already knows that she has a guy wrapped around her finger. She knows his responses to every question or situation. He's not mysterious, secure, or sexually and socially confident.
You've got to remain a little distant in order to cause some interest in her. Be a challenge, not a push over. Don't be predictable or clingy. Being at her every beck and call is only going to hurt your chances.