Well...
You say you're not good enough for her. I'm not trying to say just what you want to hear, but that previous statement is probably false. I would've said I wasn't good enough for my current girlfriend 2 years ago, but "good", along with beauty, is in the eye of the beholder. Anyway, she probably thinks highly of you if she likes you, no matter what you think of yourself.
Also, I only had one girlfriend before my current one, too, but that doesn't mean your interest in other people should be less valid than someone else who has had 20 "relationships" before they're done with puberty.
Another thing: Paraphrasing, you say she's the most beautiful and nicest person you've met. Might you have an attraction to her just for those things? Have you thought a long time about whether a relationship between you two will work?
One last thing, then I'll be out of your hair: you say you're shy (still paraphrasing), and you don't play this "game" much? Neither do I. I lack loads of confidence when it comes to love, and I overthink everything. I recommend just going for it and coming out with whatever you have to say to her. No beating around the bush or avoiding it, just do it. It'll work out better than waiting for the "perfect" time to say it.
I am homosexual. A lesbian, actually. If you have a problem with that, then it sucks for you. It's not your problem. It's not even a problem. I quite like it this way.