I have one on one lessons with my guitar teacher up in a music room at school.We have gotten on pretty well for a year and a bit, and I always had a niggling crush on him at the back of my mind, but never really thought about it.

Last lesson, I was crying before he came in (because of family circumstances), and he saw me and we talked it over. We both got quite involved in the conversation and I told him stuff I hadn't even told my best friend.
He said things would get better and I put my head in my hands, then turned towards him, he moved a strand of hair out my eyes and then I kissed him.

To my surprise he kissed me back for awhile, then I grabbed my guitar and left without speaking.
It was weird but it didn't feel wrong..

Should I go back next lesson, should I tell someone? I am so confused.

you should not tell b/c that could get him fired, i would just not do it again.

don't kiss and tell but don't let it get to anything farther

Maybe you kissed him because you felt vunerable and he was something manly to protect you?
Have a proper think, do you love him?
Or was it just a moment thing?
If you are under 18, and he is over 18,I'm not going to patronise you, but have a serious think about doing anything else, or going any further, because if you get found out, he could get in big trouble.
He could get fired and banned from working with kids and maybe even imprisoned if you do anything ***ual.

My advice to you is to wait till things have settled down at home, so you're not under the influence of any unusual emotions, and then follow your heart.
If it leads you to him, so be it.
Good luck with whatever you choose

Don't tell anyone because you will get your teacher to be fired and you yourself will be in trouble also. Perhaps your teacher likes you too or maybe he might be taking advantage of you, so be careful. Don't do anything intimated with him, don't let him takes advantage of you too, protect yourself. =>