First off, don't admit to committing crimes online or even at all. Second, it doesn't appear that you've been caught or charged yet. It's hard to tell what the store can do and will do about it. It will probably investigate the loss and review information (and any video) about it and then maybe call the police. Note that only the police can make an arrest outside the store. Note further that you do not have to talk to the police at all. If you are arrested, then, due to your age and the possible charge, you will be summoned to juvenile court. In that instance, you will need an attorney.
I doubt it, however I would not go back to that store EVER. What is clear to me is that you are a young person who may benefit from counseling or therapy. In my experience shoplifting is not a one time thing. It is often a symptom of a larger problem http://en.wikipedia.org/wiki/Kleptomania and eventually you will be caught and prosecuted. Not to add to the paranoia, but there really are cameras everywhere. I would encourage you to discuss this situation with a trusted adult, preferably a parent.
DISCLAIMER: This answer and any follow-up comments for general and educational purposes only and do not establish an attorney-client relationship. This answer is not legal advice and does not constitute a consultation. You should always consult an attorney who is licensed in your jurisdiction when you have a legal question. I am licensed in the State of Connecticut.