Teenager with a mirena?

Hi I'm new to the forum, and I wanted to find out what other peoples mirena experiences were.

Now that I've looked, it seems a lot of people who have them have also had children. In fact, even on the front of the information booklet I was given it had a mother and a child. I know I got it because I'm not good with pills and used to have 23 day, painful cycles. I was just wondering does anyone else young without children have a mirena?

Im 18, have never had children and have recently gotten a mirena (last month) and its still spotting and cramping every day- which I hear is normal if I can feel the strings, so everything is fine. I had to be knocked out to put it in, did anyone else have to do this?
Also, most of the stories I've read are horrible frightening stories about how women didn't know something was wrong, or did and couldnt do anything about it- has anyone had a problem that they simply identified and dealt with before anything bad happened?
What symptoms do you show when things go wrong?