I Am Not Exercising But Still Feel Pain In Abdomen. Why Is It ?

My abdominal muscles hurt as though I did 200 crunches or some other physical activity, but I haven t done any exercising in at least two months. Why do they hurt? I m a 19 year old female with a healthy weight, and healthy eating habits. I d hate to make an appointment with my doctor if this is something trivial, so I thought I d post my concern here. Just 10-15 minutes prior to the pain, I decided to try a diet Coke (I usually stick to water, milk, or 100% juices). I doubt there is any relevance, but I can t think of anything else I could have done that would have caused any pain. Thank you for your time.