Anita you taught as well?
Let it be known that I am also one of those ex teachers still suffering PTD from my time on the front line. It was absolute hell for me, with brief interludes of joy and reward. I taught elementary for 9 years mostly grades 3,4 and 5.
My advice?
Watch the movie Kindergarten Cop with Arnie Schwarzenneger. It proves that that there is more than one kind of tough. You need to be mentally tough for teaching, have stricter than normal boundaries and be extremely well organised. Think Mr Nice Guy works? No way. You need to present a new you, one who doesn’t smile too easily. Also the principles of training a dog might help. Incentives plus correction. Kids get your attention when they are behaving well. Unacceptable behaviour is dealt with swiftly. Time out or withdrawal of rewards. I think Kindergarten is the hardest because their attention span is so short.
Re voice. I had/have a mousy voice. Join a public speaking group like Toastmasters and learn to project not only your voice but your whole body and soul. Also sing in the car and shower. Vibrate the lower tones in your throat like a Buddhist monkl chanting.
Ok that should help. Good luck. remember you are not the first person to make mistakes in teaching. We’ve all been there.