Is there such a thing as a chocolate addiction, and would that be bad for one's health?

Yes. People can become addicted to almost anything. Eating sweets such as chocolate is immediately soothing which is often seen in people with food addictions. The question you should ask yourself is,whether it is interfering with your life or,your health. Is your weight and blood sugar ok? Do you miss work because of binge eating,chocolate the night,before. If so, talk with someone.