I think the best course of action would be to look for and secure another job before quitting this one.

In the meantime, set some boundaries about your availability when away from work ... Even if it's turning off the phones and computers for 4-6 hours so you can have a little downtime and enjoy some peace and quite with your family and get a little rest.

Your bosses and co-workers may grumble a little at first, but as soon as they see you are serious about needing and deserving a little "me" time, they'll adjust.

Again, don't quit until you've got another job, that would be tragic, but just knowing that you are doing a few modifications to your availability while looking for something else, most likely will ease a bit of the stress, depression and tension you're feeling.

Sincerely,
Pfrog!