I'm a junior in high school so this was my first year I could go to prom. No one ended up asking me to prom, but I wasn't that upset about that because 1) I understood I could go to prom with friends and still have a good time and 2) I was 99% sure I wouldn't get asked anyway. However, turns out all of my friends decided to go with other groups so I couldn't go to prom even if I wanted to, and that really hurt me; it made me feel like a nobody with no friends. And what made me most frustrated was the fact that even though my friends knew I wasn't going to prom they would always talk about it during Lunch at school, and it felt like they were rubbing it in my face (by the way I had asked them if I could go with any of their groups and all of them said their groups were too full). Now it's prom night and every time I go on Facebook I see a prom picture and it makes me feel like a complete loser.
Am I overreacting? Is prom really that big of a deal?

Prom is just one night of your life. Right now it may seem like a huge deal, because at your age that's really the biggest thing that's happened. But in the long run it's nothing. Heck, I barely remember my prom, I can't even tell you what color my dress was, or the name of the boy I went with.

The thing is, you chose not to go. You could have found another group, or tried to start your own, but you chose not to. It's not fair for you to be mad because others decided to go.

So be the bigger person, comment on their fb pictures (nice comments), listen when they talk about prom, but don't be jealous or upset. Really, in the grand scheme of things, prom is not important. Graduating college is a big deal, starting a career is a big deal, meeting the love of your life is a big deal, getting married is a big deal, having your first child is a big deal. Prom doesn't even come close in comparison.

Oops! You must spread some Reputation around before giving it to Alty again.

I have nothing to add. That is great advice.