Very upset... what do i do?

so i went out with the most amazing guy ever. it lasted for 5 months and things were great. he liked me very much and i liked him a lot as well. the day before spring break, he broke up with me for no good reason. of course i was heart broken. it was hard for me to go on with life. i couldn't get over it. i felt maybe we just needed a little brake for a while. so 2 months went by and i thought things were okay- and i really wanted to go back out with him. nope. he still wanted to be friends. (lame) one night at our band banquet i thought we could talk and see what happened. i was very upset when i saw him with another girl. he knows i dont like her. she is such a fugly slut. it is very hard to see him flirt with her every day cause i thought he really liked me. but i also have a good feeling their relationship wont last. maybe he would come back. should i wait for him? if i be a good friend and support him, do you think he will realize i was always amazing and he should have never left. could he still have feelings for me? how long should i wait- i love him very much.