Suspect that you like him as a potential partner and he treats you like a fwb (or does not care enough), resulting in you being emotionally attached to him, and giving in to his requests for sex even though you have chosen to break off.
If really want a clean break, best is to block every platform. Unless you are colleagues then a bit difficult
Just my thoughts, don't have the full story so can't really get an objective view
Maybe more facts will help. Not sure if you are seeking advice or just people to rant to