You need to see a Doctor as soon as you can...there are several possibilities. The most common reason for whayt you mention is that you could be experiencing lactose intolerance. Lactose is something found in dairy products like milk, cheese, ice cream...and yes, chocolate ( milk chocolate esp) You can try Beano, its in liquid or pill form and is usually available without a doctor's order in places like Walmart. It contains an enzyme that helps with digestion.My grandmamma suffered from lactose intolerance and so do I. She swore that chewing fennel seeds helped her, but I am not reccommending you try it.
Most important of all is to go see your Doctor as soon as you can. Things like what you are mentioning are NOT normal and you need to make sure nothing dangerous is going on.
Hope this helps you. ~A Dallas RN~