Why do i have a boyfriend but i still miss my ex?? :/?

So my ex treated me like ****... and like he would not hang out with me alot and stufff and he would talk crap about me to his cousin alot and all these girls came to me and said oh your boyfriendd is flirting with me and blah blah blah... Sooo i broke up with him .... And now i have a new boyfriend and he treats ,e soo good its like magic.. but then i always see people with my ex in like pics on facebook and i like cry and get upssett i miss him but i reallly am starting to love this new guy..WHyy??? what do i doo!?? :(