Break up problem :( please help. desperately need an advice?

my ex and i broke up a lot of months ago because of another girl so while he was in a relationship with her he would text me that he misses me and stuff like that. after a few months i decided to get a decoy boyfriend (fake boyfriend) to get his attention. i had 2 decoys. one was a friend of mine he doesn't know. he was hurt after hearing this but he never backed away. he still makes sure that i'm alright and we still talk to each other quite sweetly. i had another decoy but this time he backed out on this because they know each other and apparently this decoy (he thinks) is better than him. after that he started to treat me differently. he never texted me and whenever we talk we with each other it ain't sweet anymore. then his girlfriend dumb him for another guy and he starts flirting with any girl even though he doesn't know them and my friend told me that he was going to court her but they hardly know each other! boy psychologist out there T.T i know i sound crazy and i shouldn't be thinking about him but please just explain his complicated mind to me...it's like i barely know him