Boyfriend ex girlfriend reconciliations can and do happen. If you've just lost your girl and you really want her back, take heart, getting back together can happen, no matter how hopeless the situation may seem right now.
To be honest, it will be somewhat easier to get your ex back if you didn't cheat on her. If you did, it may not be impossible but it will be a lot harder and probably take more time. I mean why would someone want to be with a guy they know they can't trust?
Your girl has already opened up once and trusted you and let you in, and what did she get for it? A broken heart. If this is the case with you and your ex, don't give up, just be willing to give it a lot of time and you must have a lot of patience.
If nothing quite so painful has occurred between you and your ex, you will probably have a little easier time. Still, it will take time, patience and love.
The first thing you should do is to give her plenty of space. You don't want her to see you as needy or clingy. Give her enough time and space to actually miss you and face the fear that she may really have lost you for good.
Once that time has passed get in touch with her and ask her if she would like to meet and catch up. You don't have to make it seem like it is going to be some serious conversation or she might not want the drama and might refuse to meet you.
If she agrees to meet you, keep things fun and easy going. Do not discuss the past, except to remind her of the good times, and just have fun and let her see you in an easy going fun loving way.
This simple method is the best boyfriend ex girlfriend reconciliation strategy around. It can work, good luck.
Give her enough time and space to actually miss you and face the fear that she may really have lost you for good.