Excessive studying habits eating away at me

I am scoring within the top 5-10% on all my exams but I feel like my studying habits are excessive. I usually start studying for an exam three nights in advance, I will do two nights in advance if I feel more confident about the material. My main method is to rewrite my notes, essentially making my own studying guides. I review powerpoints and read out of the textbook as well. I work in 30 min intervals with at least 10 min of break time in between. The way this is working out I am studying for a combined 3-8 hours per exam and it is kllling me.

This is not a habit I can sustain for very long. My major is rigorious (pre-med/PA), but it is pretty clear I should not be spending this much time studying in my undergrad.

Does anybody have any tips? I was thinking about trying to study 20 min a night for every class and trying to get all the material locked down as soon as it is presented to me.