I'd go a lot further: take a day off tomorrow, no matter what the work schedule says. Of course do that after telling the boss that you're exhausted and unproductive due to overextending yourself with multiple 16 hour days.

In an agile, healthy work environment, this shouldn't even count against any leave budget given that you just gave them 6 workdays for the pay of 3.

Beaurocracy can complicate things and make it impossible to do that, but at the very least your boss should agree to let you go home early. If you get any negative feedback about this, I would seriously consider looking for a better place.