I've found out my ex girlfriend has recently broke up with her ex, and I can't stop thinking about her all of a sudden. I've been with my new girlfriend over 6 months now and I'm confused as why this would happen

That's because you are stuck on old feelings, when you should let them go, and not dwell on them. That's the way it is with exes sometimes, any news no matter what it is, good or bad will stir those old feelings up back to the surface, where you can feel them again. They will fade with time, and I think its very normal to have them, but for now you just keep doing what your doing, and enjoy it.

I think it's normal to have some flashback feelings when your ex is available again.

Fight the urge and try to remember why you broke up. She's your ex for a reason and you need to leave it that way.

Major point, right here. Great, sound advice.

I've seen a lot on here that says its hurt ego more than anything else I don't really understand this saying, or what it means

The hurt ego thing means that its your ego that wants her back to prove to yourself that it could work (if you understand) And as some body already said above she is your ex for a reason! People only tend to remember the good times! Only you know what is right though!

Hope that's not to confusing lol

I understand but it was ages ago now so I don't understand why its happening now

Its perfectly normal in my experience. You never forget the people you're close to and love, the feelings just fade away with time. You've just stirred them up, but as people have said, just ignore them and keep moving forwards...

Dude,

So tell us what's up with the present girlfriend that you have been with for 6 months, Is she a piece of crap, a big fat pig,smells bad,no teeth,longer under arm hair then you? Perhaps she is uncaring, abusive,lazy,non-bathing,really long nose hair.
I just trying to think how bad this woman must be for you to throw it all away for an ex that obviously choose not to be with you, and was going with another man.

Fair point answerme_tender

We sometimes miss what is standing right next to us because we are so busy looking over our shoulders!

You need to fertilize your own grass instead of thinking of jumping over to someone else's lawn.

Asswerme_tender you hit the nail right on the head bro!