I dont know what to do ?

i could make this long and i could explain you this in a very long way,but to save your time and mine i'll make it simple and short. Its over,she obviously ended it because she probably likes her ex as you said or someone else. No its not your fault,its just the way life is,let her go because she left you cause someone better is going to come into your life. Maybe not today maybe not even tomorrow but soon she will come and everything will be alright and so if you accept that its over then all you have to do is first let it all in,take all the pain that your feeling and let it in. Cry your heart out,its okay to feel pain in fact it shows you that your alive and your doing well. after that understand the pain,you have to really find out whats hurting you inside is it really hurting because she left your or are you hurt because she might have left you for another man or etc. and now finally let go of your pain. Just leave it all behind whatever happened it happened for a reason,you'll find out soon it may take some time but everything should be alright again and you'll feel even better so let your pain go and just forget your past =]