Leave him, he's apparently in to someone else.
If your ex likes you so much you should ask him one last time if he likes you, and ask him which girl he might want to go out with.
Boys can sometimes be confusing..............unfortunetly I have been in this same position as you are or were...........try asking him or see what his body language says
Find a nice hobby to refocus your attentions.
Try talking with her to find out the truth.
the way she acts around you when she see you
she likes him too. get over it
Find another girl that you like that DOES like you.
She might not be interested in you. Just because she knows you like her doesn't mean she will like you back.
then most likely it is just a little crush, and she wont break up with the guy for it
Wait and see what happens.
Then move on. If the girl has no interest in you then you shouldn't worry about it.
Ask.