how does someone online track another persons web activity? when they may not be a internet provider?

basically someone has accessed a lot of information from me, via internet use. websites ive visited, and things i followed on my \*PRIVATE\* social media accounts. its sort of scary. maybe he took info from my page before i made it private. but..

this person is a web developer, designer, programmer. he knows how to optimize for websites . SEO- basic stuff. but hes developed websites and done things in IT so he has a history in security/privacy. and even …

accounts basic designer developer info information internet may media privacy private programmer scary seo social social media sort things web websites