Am I making careless errors or real knowledge gaps? (slips vs mistakes)

Here's a quick test: redo the questions you got wrong, untimed. If you can solve them correctly, those are performance errors (slips), and the fix is better habits and pacing. If you can't solve them even with unlimited time, those are knowledge gaps (mistakes), and you need to study the underlying content. Most students have a mix, but the remedy for each is completely different.