You don’t get notifications for people following you, so you you should check out your followers list to see who can read your posts.
Facebook is not just about friends. It’s about followers too. You can follow people without adding them as friends and they can do the same to you.
Neither you or they get notified about new followers, so you could have a long list of people who follow you without you even knowing.
So how can you see who’s following you?
If on the web version it’s easy, on the Facebook mobile apps you need to dig a bit.
Obviously, the info is found on your profile profile page. So open your own profile on the Facebook app.
Now tap where it says “See your about info”. It doesn’t look like a link and that’s confusing. But taping that line opens a new page about your profile.
Scroll all the way down on that page until you see something about followers. Tap see all to open the list with all the people that are following you.
From there you can block the follower you don’t like, but the subject for another article.
Keep in mind that follower can only see your public posts.