If you can get your ex to tell you what made him feel you were too clingy then you are in luck. Take what they said and analyze it. Maybe you were around too much or getting way too “up in their face” about every little thing. Perhaps even go as far as to say that you were becoming a bit obsessive with them.
Then you must sit back by yourself and think about how you weren’t leaving your ex enough space before the break up. Also be sure to find out for sure that your ex wasn’t just saying this because he wants to date other people. It is an all too sad fact that the line “I need more space” is just another way of saying that they want to date other people besides you. When asking your ex about this possibility you must make sure to be as kind as possible and to ask for complete honesty. Because the fact of the matter is that if your ex truly wants to date other people then you have no chance of getting back with him while giving him his space at the same time.
If that isn’t the reason then just say okay and go off to think about how you were inflicting the amount of space your then-boyfriend had. You will most likely be able to think of a few things that caused the decreased space but most likely you will need to hear from your ex what you were doing wrong. Only then will you be able to fix what went wrong.
The next thing to do, or shall I say not to do, is to call your ex a million times or send a thousand emails begging for another try. You will again be effecting his amount of space and driving him farther away. Instead just send him an email or a single text stating that you need to talk and for him to get back to you whenever he can. Once you get him around to sitting and talking with you find out how to fix the space problem. Find out how you made him feel he had no space left to breath and how you can fix it. Only then will you two be able to move on and get back together in a new light.