How come my bf can see all my likes/comments/posts on Facebook?

[TuTu]

It definitely has to do with the Privacy Settings. The best way for you to understand is going through your own Privacy Settings. From there you will know up to what level and in what way you can block/allow other person to view your activities. But do bear in mind, it could be the girl(s) (whose photos your bf 'Like') added your bf but not you, and that this girl set a privacy that only 'Friends' can view her activities (including Photos, comments). However, the best is to talk to him face to face rather than checking your bf in this way, there could be misunderstanding by simply judging from his 'Like'.