Well, it's a pretty unhappy place to be when you've been left on the curb and it wasn't even you who wanted that. And what's going to make it worse is dwelling on it. But you'll have to think it over if you want a second shot together. If he doesn't mean that much to you, then you probably wouldn't be here asking why your ex boyfriend dumped you.
You might as well look at him first. Face the facts that some men just don't know a woman from a fire hydrant and they'll always be a little clueless. Other guys just can't handle commitment. Some guys make a great short-term fling, but a lousy long-term. And so on. You might also ask yourself if he's really worth having back at this point - if he has character flaws that came between you in the first place, they're only going to get worse and worse as time goes by.
In asking why your ex boyfriend dumped you, you should not give too much weight to what he said the reason is. He might not have wanted to hurt your feelings or he may not have been able to express the real reason to you, so he used a stock, pat line like "We outgrew each other." Yes, thinking about this is guaranteed to drive you a little crazy, but if you find something glaring that you know is what the problem is and it's something you're also in denial about, all the web articles in the world can't help you.
Were you too clingy, possessive, or jealous? This can wear down a relationship over time, just because a man gets tired of having an argument every day about the same thing. Being too clingy is a sign of low self-esteem and jealousy is a sign of insecurity. You'll have to deal with these issues on your own, before you worry about whether you're back with your ex boyfriend.
Or perhaps you were nagging, demanding, and hostile? That turns a man off even faster. It's true that some men expect to provide for their woman's comfort, but some guys get burned out with a woman they think of as being hard to afford.
While you're asking why your ex boyfriend dumped you, you could also consider whether you were attractive to him. Now, we're all born with certain looks and traits, and that's all we get so we have to deal with them. But even then, TV makeover shows have shown us by now that there's a lot you can do with what you have. Remember, it isn't so much a matter of what you were born with, as much as whether you take good care of yourself. Think in terms of being healthy and having good hygiene, and the beauty will come out on its own.