Is this teaching trauma that i have had or what?

I graduated college in 99′. I have a BA in elementary teaching. Im in NYC. Im 32, and i never had a fulltime perm teaching job. I subbed in 00 though 03 off and on and alittle in 04-5 and havent set foot in the school system since. I have been making money on the side teaching piano lessons and tutoring neighborhood kids.
I dont have a license yet but im 1 test short of it. I passed 2 of them and did all the requierments. It was like pulling teeth to get all that done and pass the 2 tests.
Jsut thinking about taking the last test freaks me out and makes me nauseaus and depressed. I like to help kids but once i get in a classroom with them i freak out and the kids are rude, nasty and dont want to work no matter how fun or how much rules i set. Its such a hard job in the schools and physically exhausting. It also gives you alot of mental trauma with the abuse the kids show towards you.
I wish i can find a nice setting . I was thinking of leaving nyc and finding a pleasant teaching environment where the parents take interest in their children and show concern.

Do you think i should just give up and find another career. ITs been 8 yrs off and on doing this and im just burnt out and i havent even really done it fulltime. I have a piano backround. What should i do with my life now? have i been traumatized and am i done? I just feel sickened by the fact of going in a class room or setting foot in one. BUT i love to help older HS students and look out for them. I like to mentor them. But i cant deal with 30 of them at a time. Is there any career that i can use my teaching degree and still help kids 1 on 1?
Im all pooped out.

PLease tell me what i should do next? Why have i been sickened by this career

thanks

Become a music teacher at a private school.