I can understand how you're feeling. Im a girl, in year 11 so presumably same age as you if you've just had prom. Rejection hurts, especially if it's done again and again and if you make improvements to make each time better and decrease chances of rejection, like talking to the girl more, asking out differently etc. It feels like all efforts gone to waste right. Especially as you've waited so long for this particular girl only to have her taken by another guy.
You have to remember that at 16, you don't have to have someone. Society teaches us that falling in love is a means to an end, like love is the final destination in our lives. The disappointment comes from the thought that because these girls have said no, you won't get that final resolution ever. You will. At 16 you haven't fully developed mentally. You might feel old and like you have to have everything perfected but we're all still children. There's 20 year olds, 30 year olds who don't have their lives sorted. You can still be single and function happily.
I went through year 10 feeling terrible because nobody seemed to want to love me. I fixed this by telling myself just how young I am and just how I don't have to have this all sorted now. Once I relaxed and settled into life accepting no guy loves me, I suddenly came out having two of the bestest guy friends I could have because I had accepted that nobody at 16 is ready to date, and so I had begun to see the bigger picture. And so what if they don't want to kiss me? They love me for who I am, and that's all I ever wanted.