Though he only sees me occasionally (at parties), he continued this behaviour of watching me as I eat or drink or hides behinds a door and watches me as I walk. This went on for almost 5 years and I couldn't yell out and tell him off since he always stands afar to stare at me.
It's been 2 years since I saw him and a friend told me that he recently got into another relationship. However it turns out that he still uses some indirect mechanism (perhaps coding) to make sure that even the posts/pics he uploads of her (which are visible to the public) are hidden from me. Fb doesn't have this direct feature to hide a public post so he used an indirect mechanism to achieve this. I got concerned so I blocked him to see how he'd react, and he almost immediately got to know I blocked him (by stalking my fb profile) me) and he instantly 'unhid' those posts. Given the whole story, his unhealthy behaviour bothers me and I somehow feel responsible. What can I do?