How do I get back together with my girlfriend?

We broke up over 3 weeks ago. I told her she's "not the one". The next day she dumped on my doorstep all the gifts I gave her when we first started dating and told me to lose her number. We haven't talked since. I made a huge mistake. I really love her and want her back. But if nothing else, I want things to be alright between us. What should I do?? Is it too late?