You are not a failure, and you are not worthless. You ahve had time off to get to know yourself, and you know yourself better than to say you're a failure. better to know now than a month down the road that they all suck.
My sister went back after a mat leave of a year, and quit her first job in a few days. It wasn't the right fit. You may not see it now, but that was also not the right fit, right??
Chin up girl, you can find something way better. it's just the beginning.