Chocolate

For the past three weeks I've had an insane craving for chocolate. I keep eating huge amounts of it but it still isn't enough and it's kind of freaking me out. Last week on wednesday I had the worst craving for it ever. It was so bad that I had to almost run to the vending machiene. While I plugged in the numbers for a reeses my other hand began to shake literally uncontrollably and I began to feel sick. I've never ever had that happen to me. I know that i'm not the only one in my familiy that craves chocolate, my aunt eats one or more chocolate bars every day and my grandma always has tons of chocolates in one of her cabinets. Could this be a hereditary problem? Am I maybe lacking something else in my diet? Does anybody know what's going on with me?