Why does my ex always seem to know where I am?

my ex and i broke up he said that he wasnt ready for a relationship. but a few days ahead of time asking if i love him. now he seams to know were i am and shows up he constantly looks at my facebook and snap so does his brother. i found out that after we broke up he kissed his freind because he broke up with me he always want to go to the club with us i dont know what is going on with him help.