Hi there!
Its a hard one, I think.
I'm 38, and was baptised 2 and a half years ago after having been a Christian for 20 years. I had been baptised as a child, and it took me a long, long time to figure out all the theological wrangles of that - finally decided that I wanted to do it as my parents got me "christened" with no real intention of bringing me up in the church, though we did go sometimes.
I think it is something that it is good to do, however, it doesn't make you any more a Christian than you were before. Though for me it was very emotional, actually. I thought I was just doing it cos it was something I should do (we had recently started going to our Baptist church, couldn't be members if not baptised, and for the first time ever, in a church that didn't promote Infant Baptism).
I stood in the tank, and though "why am I doing this?", went down, and came up dripping wet but also sobbing my heart out - it was a very, very emotional thing to do. Partly I think as we had our 3 children dedicated on that day and dh was baptised just before me.
You were clearly very badly treated as a teenager over this. Personally, I wouldn't want to see anyone under the age of about 16 baptised, because you need to grow up and make your own decisions. Have you talked to anyone about what happened to you? It would be good to talk it through and try to learn to come to terms with what happened, which might well include forgiving the people who put so much pressure on you when you were so young and vulnerable.
It also really sounds like the church you are going to is not for you. You don't have to say, but your talk of precenters and psalms makes me wonder if you are in the North of Scotland somewhere? I lived in a very "Wee Free" area for a long time and it can be quite difficult if it is not what you want. I don't think you should be baptised in a church you are not happy with, where you don't belong. I spent years in the Church of Scotland and more years in the Scottish Episcopal Church, but now I am in the Baptist church I feel I have really found a 'home'. I know what you mean about the tunes and the jeans and the dancing - I'm a big old happy-clappy, me!
If you would like to talk to me more about this, feel free to CAT. There are a lot more personal things about the whole experience I would not want to put on a public forum.
Take care, and just spend time getting to know God better. there is an ancient Celtic blessing which encourages you to "sail into the ocean of His love" - this is my prayer for you.