Apparently I should just "know" and if I don't know - I'm wrong for not knowing
So, the reason abusive people will never give you a clear, comprehensible reason for what you've actually done wrong is that they can't, because there isn't one.
You haven't done anything wrong, you've said or done something that resulted in them feeling bad or particularly, feeling bad about themselves.
You might have reminded them to do the dishes because it's their night and they're not showing any signs of moving to do them. You might have mentioned that you like a particular movie that they hate because they were once told that they look like the 'nerd' character from the movie. You might have been having a conversation about a current issue and your perspective differed from theirs and your reasons why made more sense than theirs. You might not have responded to a very subtle overture for sex. Or they might have wanted you to make an overture for sex but you didn't. You might have been reading out interesting lines from a magazine article and although it was annoying them, they didn't ask you not to do it the first time you did it, so they sat there getting more and more annoyed each time but not feeling like they could say anything.
The reasons they feel bad are many and varied and hard to predict, but you will be expected to "just know" what you've "done" (or not done) because abusive people have trouble understanding that other people do not see the world exactly as they do.
When they try to put how they're feeling into words, they either can't, because they're very bad at identifying feelings, or if they say what they're thinking out loud, the unreasonableness of their blame towards you becomes quite obvious.
So they dance around it, say "If you don't know, I'm not going to tell you", tell you "You're just being annoying", "It's a bunch of things over the past few days" "You're having a go at me all the time" or whatever non-specific phrase allows them to vent the bad feelings onto you and make you feel obliquely responsible and start apologising, soothing them, fawning over them, doing what they demand, etc.
If someone has a pattern of getting mad at you but not giving a clear and comprehensive reason why (ideally along with a suggestion of what they would have liked to happen differently), then they are either abusive or have very significant emotional or mental problems. Either way, it's beyond your capacity to solve – they need professional help. The best thing you can do is leave the relationship, because if they do truly care for you, the upset of losing the relationship may be the trigger for them to seek professional help.