[Sage]

In the immortal words of Barney Fife, "Nip it in the bud!".

He is taking the fact that you have yet to tell him to stop bugging you in no uncertain terms as implied approval of his actions.

In situations like this, you must be absolutely clear about how you feel. Tell him point blank "Stop following me, stop calling me, and stop messaging me. Leave me alone". If you don't, he will only get worse.