her getting with another guy that quickly is so fucked up. don't take that shit to heart, she's the one in the wrong 100%.
you just need to figure out how you want to address the pain. do you want to take it head on and work through your emotions? or would you rather take the "toxic" route and view every success of yours as a way to prove to yourself that you're worth it and better than her? i've had both mindsets and it just depends on where you are in life. breakups fucking suck, i know, but feeling sorry will not make the pain go away. take small steps to improve your mindset, go on walks, talk to friends, go to the gym, etc. delete any photo or text you have of her, it won't make you feel better. focus on yourself for the next week or so, you deserve it.
i hope you feel better bro, if you wanna talk about it more just dm me on vlr. <3