Definitely don't do this. My advice to you is never go back but if you're absolutely certain you can't kick your oneitis for this girl then this is what you must do;like showing unannounced at her door? Hug/ kiss her saying I want you. ?
1) No contact - this isn't the 30 day no contact b's you see on YouTube. This is indefinite no contact initiated by you. No texting, emailing, calling, stalking (online or otherwise).
2) level yourself up - work out, eat better, become wealthier. Read, write, learn.
3) date other women - essential. This builds confidence and self-esteem. Don't be a d1ck about it and post this all over social media as it'll just make you look weak and like you're trying to get to her.
4) find a way to showcase how much you've grown in a covert way. Never directly tell her anything about your life but if a mutual friend were to drop it in conversation that you're smashing it at the moment, that would more than likely do the trick.
5) if she's still your mental point of origin, this needs to change or you'll get her back but on her terms and in her frame. Not a place you want to be.
Note - This can't just be an act. This must be genuine change and the bonus is, once you do the steps above, you'll most likely realise that she was the one punching anyway and you won't even want her back anymore then you go and find someone better/hotter/more fun anyway.
But personally, I'd disregard all the blue pill "advice" I just wrote and move on.