aw cue man, she didn't deserved you ! like ramone said, you are a very nice and special person and we all like you.
keep your head up, think about it and processing it... no matter how long it will take (be strong!!!).
it will be not easy, but time will heal the wounds. take deep breaths, if you are upset because of this and clear your mind of bad thoughts.
i don't know the reasons... but i am very sure, you haven't deserved it cue ! care for your daughter...
sure... she is the mother of your child, but at least you can say to your daughter, when she grown up to a young lady...
you always did the right things, what your ex-girlfriend can not say of herself !
life sucks sometimes very bad, but you must get over it... as fast as you can !
i'm wishing you all the best and good luck. make your own peace with that and better times will come for sure !