How do I stop crying?

Yes, it hurts. And it may hurt for a while, we all heal differently.

Now go do something for someone else. See what you can do for someone who is worse off than you are.

I like that suggestion

Rejection is painful, isn’t it? I promise it will pass.

In the meantime, there are many things you can do to distract yourself from the pain you are feeling. Here are some suggestions:

-cuddle a pet
-watch a movie or tv show with a friend
-learn how to juggle
-listen to relaxing music
-go run 5 miles
-learn how to shuffle a deck of cards
-bake a pie
-read a good book
-play the new Zelda game
-go for a walk
-clean up litter in your neighborhood
-clean out your closet, picking out and putting aside clothing and items that can be donated
-buy some modeling clay and make figurines

The crying stops when you are done.
You have great suggestions for diversions from @zenvelo and @cinnamonk. It is good to find other directions to focus your attention. Still, at night, when it is just you, the dark, and your pillow, the tears intrude.
It may seem callous of me for saying, but you will hurt until you are done, and there is no hurrying the pain away. It is a healing. When you skin your knee, the wound will be there a while, and you might want it gone, you know it will be gone eventually, but for a while, you are stuck with it.
You will be stronger afterwards, kind of new, in some ways.
The bad news is, it will happen again, sometime.

Aww…I feel for you.
I’ve been going through something similar only it was my wife and she cheated and then dumped me.
We have a child together too so I guess I’m saying at least you aren’t married to him with children, it would feel like the end of the world.
For what it’s worth he sounds like an asshole for doing that to you and I really hope you find someone better.

Same thing happened to me. Eventually we get over the hurt. It’s ok to cry for a while but you can’t let it consume you. Best thing to do is move on with your life. Relationships come and go. If someone is truly meant to be with you’ve they will find you and stay.
Continue doing things you enjoy. Write down how you’re feeling.

One calm breath at a time. One calm second at a time. One calm hour at a time. Maybe a day. Then a week…. And so on.

You control your body. Not the other way around. Pull yourself up. Breathe. Center yourself. Understand that what you’re feeling is sadly, a normal human feeling, from a common human situation…

Don’t be afraid to share your feelings with your closest friends, and family. “We all need somebody to lean on.”

You’re not alone.

You can get through this.

Good luck.

Peace n love.

Just wanted to add that I agree with @Danebiggs – this guy is a total jerk! Hopefully that fact will help you move on quicker. It’s not like you have lost anything worth keeping.

There’s something missing here. I would like an explanation concerning “things were going great”. Do you mean the 2 of you were involved romantically? Committed?

It sucks. It really does.
When my ex and I broke up, I started stitching. You don’t have to stitch anything beautiful, just take a piece of fabric, draw a line, and stitch on the line. Something about stitching is very calming because it requires constant attention.
I cried a bit too. Late at night. During the day I was fine because I was busying myself, but at night all I had were my thoughts.
This might sound unhelpful but it worked for me. If you feel like crying, and nothing you do will stop you from crying, then cry. Let your mind go through the stages of being sad. I felt better after I cried and I got over that stage really quick. The only thing you should be trying to stop yourself from doing is thinking of him. Don’t obsess or prevent him from you living your life. You will get through this. Everyone will go through a heartbreak and those who have gone through it, survived. I know it seems impossible now, but you will find someone who’d never hurt you.
(I would like to add that although I said to let yourself cry, I don’t mean you should be crying 24/7 or anything like that. It is okay to cry occasionally. Try to busy yourself as much as possible, but don’t force yourself not to cry is my point)
If you ever need someone, feel free to PM me. I am always here to help.

Sometimes it is best to go ahead and cry out the pain. Then we pick ourselves up and get on with our lives as best we can. You have other friends and will have many more opportunities; don’t count yourself out yet.

Guys are idiots. Maybe he thought the new girl would spread her legs faster. If something like that is the case you dodged a bullet.

My friend in college, we will call him Bill, since that is his real name, bragged about fucking a different woman night while he was in college. Shocker, he got married and cheated on her multiple times.

Again, bullet… Dodged.

I would like women to know and learn that just because a guy has been close to you or wanted to see you does not mean he is in love with you. Sometimes you take the blame for premature judgement. As for how to stop crying, you can’t forcefully prevent yourself crying, it’s a natural expression of your feeling, and there’s nothing wrong with it except when you cry for foolish reason.

I’ve been there. It sucks. Allow yourself a good cry and then go out and do something around other people. Do something nice for yourself. Exercise—even just taking a walk—can help. It will probably take a while for the pain to go away, but in the meantime, you can still be living a good life. I hope this doesn’t all sound trite. Best wishes.

I’m not trying to sound insensitive or lessen your pain but I’ll tell you how I have handled this. (It’s been a long time so my advice might be out dated. I no longer drink either)
You get together with your best girlfriend, a bottle or two of wine (if you’re of age of course) and a box of bag of good chocolates. Maybe not even good chocolate, but at least as good as Dove chocolates. You sit at home, order a pizza, maybe watch a good comedy and bitch about what an ass hole he is and why he didn’t deserve you anyway. Maybe even look at his picture and point out his flaws. Drunk crying will happen and that’s ok. DO NOT go to a bar!
It sounds immature, I know but it has been the most therapeutic thing I’ve ever done to get over a jerk that didn’t know what he threw away.