Even though I had chicken pox as a child can i still contract shingles?

My 4 year old has a moderatly bad case of chicken pox. I had a VERY severe case when I was 11. Over the last few days I have found myself getting the same kind of itchiness as chicken pox, but as far as I was aware, if you had a bad enough outbreak as a child, your immune system could fight off any contact with it as an adult. However, I seem to be developing symptoms, including restless sleep and at the other end of the scale, exhaustion. I have a very itchy back and my temperature seems to be fluctuating between overheating and freezing cold. Do I have shingles, and if so, what are 'shingles'. Thank you...x