He was yours, you still have feelings for him, and you're asking yourself how can I win my ex boyfriend back from that girl? For some strange reason she has him now but if you believe the two of you should be together then it can still be possible.
You do need to play it smart though and be dignified if you're going to win him back.
Being nasty doesn't work.
That girl may want to play nasty as she'll almost certainly want to keep him for herself.
Being nasty in return is probably the biggest mistake you can make as all that will happen is you'll create a running fight and lets face it; you're above all that as you're more mature.
What you need to be doing is show him this mature side of you and that you're all woman, she's just a girl.
Your first instinct is to fight back - don't! Most peoples first instinct is to stand and fight, after all, she's the one that caused you so much hurt and pain.
However, you need to rise above these negative feelings and take control of your emotions.
This will just show everyone, and especially your ex, that you're the mature one and show up the other girl for the immature person she undoubtedly is.
Rather than resorting to bad language and bitchiness, show your positive side instead.
If you look to be in a much better light than she is it will again emphasise the difference between you and that you're the much better choice.
Be the better person and you'll stand a far better chance of having your ex boyfriend back with you where he belongs.
Make him see sense.
If you find out that the other girl is treating him badly then one good course of action is to talk to his friends as they may all be thinking the same thing.
If it carries on then you may be able to enlist their help and hopefully make him see sense.
When you talk to his friends, try and find out what you can all do together to try and rescue him from the situation.
It may be that secretly he wants help but feels too proud to admit it.
The secret here is to have all his friends on your side and all work together.
He deserves better.
If it seems as though the other girl has your ex boyfriend under some sort of spell find out what it is that she has over him.
You need to try and help him see that he deserves better.
Also, let his friends know that he deserves better as they may well secretly share that opinion and agree with you.
If it seems that she has him obsessed with her she might well be forcing him to spend too much time with her at the expense of his friends, and you as well.
His friends may want to see him back with them and if you're on their side then they'll be on yours.
Convince his friends you're better for him.
If you're able to convince his immediate friends that he's better with you then you'll have a lot smaller struggle going on.
They'll see that by helping you get what you want they get their friend back as well.
There will end up being so many people against him that his relationship with the other girl will most probably fail.
The real secret here is to be the power behind the scenes and let others do the actual work out in the open.
This way, if the other girl catches on to what's going on you can make it look like it's just her jealous nature trying to make it look like you're the one causing problems.
Friends need friends.
The overall objective is to win your ex boyfriend back and to do that you need to have as many people on your side as you can.
If you start off looking at it as though it's only you against the two of them you're going to struggle.
By getting as many people as possible, such as all his friends, on your side then it will end up being those two against the whole world.
Once the relationship with the other girl falters, you'll find it so much easier to win back your ex boyfriend.