why does it hurt so bad?

Begin the healing process by taking things that have significance to you and throwing them away. Take them and tell them that they can't be a part of your life anymore. Every time you have an item (it doesn't even have to be a physical thing), tell it something. "I can't keep you anymore because _______"Stay positive. You're still young and there's still plenty of boys out there. :)

You're not overreacting. At that age the smallest shit looks ginormous so I'm sure this is pretty devastating for you.

Anyway, you'll get over it - will just take some time. Maybe a few weeks. It hurts because the little shit went and already got himself a new girl so quickly, so it probably makes you feel less valuable or like he didn't like you as much as you thought, plus 9 months is a long time. But 14 years is also just the beginning, you're still maturing and learning about who you are as a soon to be woman. Peg yourself lucky that you've experienced the pain of a break up now so that when you're more mature and move on to a new relationship, you'll know how to better handle it.

If he has found someone else so quickly, then he isn't worth your pain. You'll eventually get over it. Find something else to get attached to, like a hobby, and get your mind off him. There are other guys out there.

You're young and you got that lil puppy love. I would try my best to get over him. If he has already moved on to someone new then he was talking to her ahead of time. No one moves on THAT fast. Also, if he's moved on, you should too. No point in moping over him when he's happy with someone else. You need to move on and get with someone better whenever you're ready. Don't rush into another relationship because that person will be just a rebound. Wait till you're fully ready to be with someone else then find someone. Until then, take care of yourself and don't be sad. Keep your head up! We all go through heartbreaks at least once in our lives.