A. When parents divorce, children often think it's their fault. Of course it isn't - children don't cause divorces. But children can end up worrying about how much they're loved. This may be what happened to you. If you were close to your father for a while and then experienced him 'leaving' you a second time when he remarried, you might feel that you aren't really lovable and that you can't keep a man (first your father, now other men).
You might now be distrustful of men and find more satisfaction in making men fall in love with you than in actually entrusting yourself to a relationship. Once you've 'won' someone's affection you turn yourself off because you're afraid you'll be hurt again. If this makes sense to you, and you want to interrupt this pattern, being aware of these underlying feelings might help you to make different choices.
If you like Steve so much, tell him how you feel, tell him your fears, and explain why you feel like that. If he's the right man for you, he will reassure you and help you deal with any negative feelings you may start to experience.