I need to stop thinking about an ex, any idea's?

Essentially…....Go out with friends and do something and try to get laid in the process, if you want.

Time plus getting a new is the combo to cure what ails you.

Every time you find yourself thinking about her, replace that thought with the fact that she cheated on you (and anything else reprehensible that she may have done during the relationship.)

Then, after dwelling on the fact of her cheating on you and why you broke up with her, deliberately turn your thoughts to something else.

Try exercising to keep your spirits up.

Consider volunteer work to take your mind off of your troubles.

Open up to the possibility of meeting someone new.

In addition to what @marinelife suggests, consider looking at meet.up.com for meet-ups in your area. It’s an interesting way to find activities and people that are interested in things you like to do.

Fahgehtabouther! She messed your mind up and fooled around on you. Remember the pain this caused you and that should help keep your eyes on the road ahead.

Not any effective ones.

Rebound.

Time has a way of healing old wounds and giving you new perspectives. Your obsession will abide and the hurt will lessen in time. Find a hobby or new friends, or go out and do something nice for someone. By keeping your mind busy, it will help you stop thinking of someone.
Also accept that you are going to think about the person until the day you suddenly don’t. You may not forget the person, but the memory will gradually cease to be painful (or uncomfortable) and without an emotional association to go with, a memory isn’t much at all.

Just keep in mind that she cheated on you every time you think of her, because that is the fact (If it is), and if you still can’t stop thinking about her despite the fact that she cheated on you, maybe you would be able to forgive her.

Don’t fight it, deal with it! It is not so much about the fact that you are constantly thinking about her that you need to change, but what you have to concentrate on is how and what you think when you think about her. To begin with, you have a heart and a mind and therefore you need to operate with both, ie heal your heart and put your mind to good use. I don’t know how old you are, but in case you don’t know it yet, I have news for you: there is no quick fix for these things and it will happen to you a few times before you actually find the right one—if ever. You need to take your time and go thru at least two stages for healing. First, you need to mourn and think about all the great memories that are now in the past. Maybe listen to some sad music to make you even sadder and cry if possible. This will saturate your system of sorrow, hurt and grief and you will eventually want to get out of that sad stage and get back to normal —much as it is when someone dear dies. If you go out with your friends and “pretend” nothing is happening, that is not going to work and you will only be delaying your mourning process (unless they are willing to cry with you). Second, when you have mourned for a while, then you need to focus on the reason why you guys broke up and how her cheating was unacceptable and how a person like that is not worth your time. Think that given the chance it’d not be a matter of if but when she’d do it all over again. It will get better. Time heals. Trust me I’ve been thru that one too many times.

One effective way is get busy doing things to help other people. Volunteer for any worthwhile projects that will give you direct contact with others who chances are have severe problems compared to yours. You will feel better, you will be as a person better and lucky is the next girl who will have you.

BTW you could start with family and friends who may need your help and don’t hesitate to do random acts of kindness. For example, when I was so distraught after losing a girlfriend I went out for a bus trip to the city and offerred my seat so this young couple could sit together. I also just bought a sandwich and before I took a bite offerred it to a homeless person lying on the sidewalk. You will feel an exhilarating rush of joy opening your heart sincerely each time. And that joy in your broken heart? That is sure to fix it.

You won’t stop thinking about her, or not for a while anyway. The mind has a fun way of bringing up things you’d like to forget (seemingly at random with me). What you have to do is just actively tell yourself to ‘Stop’ when you find yourself beginning to dwell on them. Remind yourself that there is nothing to be gained by being sad and looking back. You cannot go back and change anything. You can’t change her decisions. It’s done.

I went through a rough breakup a few months ago. There is nothing to stop him from crossing my mind a few times a day.. but I have to either shrug it off and put my mind elsewhere, or remind myself why it did not work, or tell myself to just stop it and do something productive. Hopefully that will help you too. Finding someone else helps, but in the long run, it really makes things more difficult. Get over it as best you can, and then look for someone else. Just make sure they are not filling the void left by her, or you’ll hurt both of you. Good luck, I know it sucks.

Try this mental exercise in case it’s that bad. Imagine your problem as heavy bags that you will put down for a while, leave it there as you go on about your day. You know you’ll come back for it later but you just need to be your best, luggage free while doing what you need to do without distraction. At the end of the day if you really must, then come back for those bags. Repeat this process often and chances are you will eventually find yourself not even feeling the need to go back for those bags. Goodluck human!

Thanks everyone, all your suggestions have really helped and I’ve managed to do a fairly good job of keeping her out of mind when it counts and dealing with my feelings when I can. I’m sleeping better at night and can concentrate more on my schoolwork. Thank you all again =)

@Begeara Never forget you are never alone.

That sucks dude. In the end, if nothing else, time will take care of it.
However, you can get there faster. For now, focus on your schoolwork, and get together with a hottie. Focus on how good new gf (hottie) is at doing XXX and at how lousy old gf (cheater) was at it.
Figuratively speaking, you want to get to the point where you remember your old girl as a 1985 ford explorer, and you see your new girl as a 2012 Mercedes GL550. They’re both suvs, but you’re clearly much better off both viscerally and theoretically with the Mercedes.
The thing is, it’s not about pushing the thought of her away—which in fact will likely have the opposite effect—but rather about getting to the point where you actually think about her naturally and without strain, in a different, and more or less neutral light.
Cuz when you’ve got a 2012 GL550, you’re not going to miss your old 1985 ford explorer. In the same way, by focusing on the awesome qualities of your new gf in comparison to old gf, you will not only not miss former gf, but more importantly, you won’t be angry at her (which is an ugly place for you to be), and you’ll be comfortable around her if ever you meet in the future (which is great for you, and will likely make her question why she cheated on such a cool and confident guy).
Good luck man.