Far out, I have tried to reply twice to this thread. Written out a huge post only to have it vanish. So you get the condensed version.
Don't take a job in a supermarket (or whatever). I have no issue with those jobs and can thank them for getting me out of many tight spots. But as a highly qualified mum returning to work it will not impact positively on your self esteem.
Secondly, go get your WWCC (you would need it to enroll in that course anyhow) and push, no ...shove, yourself out of your comfort zone of misery to go volunteer at the local Kindy. You may love it, but if you hate it that is still a good thing because you will have done something! You will have taken that first, oh so difficult step towards working out what you need to feel valued.