Good you're looking at moving on.

Your manager/boss at your current place has failed you. No one is to be dumped into such a situation without any support, guidance, or backup. Especially not someone like you into what seems like your first job, where you need guidance on how to manage expectations, say no, etc. Also, have you never had to fall ill, or take a vacation these past 5 years? Your boss needs to make sure someone can cover for you.

Moving on helps you start from a clean slate. But make some changes at your new place. Talk to (and email) your boss there when things get beyond your capacity. Do not get over-invested in your job. It's a means to an end to get paid, and for you to live your life.