I’ve been out of school for about 4 years and I make more than 3 times as much as he does. (I never asked how much he makes and he’s never asked me either).

So OP simultaneously knew how much more she made than him while also saying they never discussed how much they made. Ok, so maybe she just didn't know an exact figure but had an educated guess. But then...

from what I know he made about 90k when we got together

So she did know how much he made? But then...

he showed me his paycheck and honestly based on what everyone was telling me I thought it would be on par with mine.

So now she thought he made as much as her, as opposed to her making 3 times as much?

I know this isn't the main point, and obviously these 2 characters have no communication in their relationship, but I'm wholly confused by OP's own perspective.