Yes, rejection is terrrible. There is nothing anyone here can say to stop this from being true right now.
But…
You are young. The probablility is that a relationship you have as a teenager is unlikely to result in marriage, so a few heartbreaks are almost inevitable. Many/most of us who are happily married now went through these ordeals, so try your best to recognise that you just need to move on and over time understand that “there are many fish in the sea”. It’s a bit trite, but it’s very true. Keep yourself busy with whatever - sport, friends - and soon enough you’ll probably find yourself interested in other girls and forget about old what’s-her-name.
And don’t be afraid to have a bit of a cry. It’s theraputic for guys too.
