Why am I having such difficulty? What is holding me back?

If you are Ok with not worrying later about not asking her out now, she might not be that important to you. If you are cool with being alone because of bad relationships in the past, that's cool too. Your comments indicate you are more nervous about going out with her than you are about asking her out, so you might be worried that she likes you more than you like her. The prom can be a lot of fun, but if you are there with the wrong person it can be torture. This girl deserves to go to the prom with a guy that really wants to be with her and you don't sound like the right guy. Do yourself a favor and stay home and watch TV. Don't feel forced to do something you really don't want to do. Once you take that pressure off yourself, you may feel a lot better, and you will have quietly sent a message to that girl that although you like her, you don't like her enough to take her to something that should be special to both of you.