What Causes Nausea,diarrhea,cramps And Headache After Consuming Soda?

My name is Kristy, I am 24 years old. I have no history of Allergies and I don't often get sick. This year about a month ago, I had a little bit of Mountain Dew on an almost empty stomach, and I began to not feel well. I got some food in me, which helped, but then I took a downward turn. I felt nauseas, had a head ache, some cramping, and diarrhea. 3 days ago, I went to a movie where I had popcorn and soda with my sister. Within an hour of finishing the Mountain Dew, I began to feel poorly. When I got home, I tried to eat, but it didn't seem to help. within 8 hours, I was again feeling nauseas and everytime I ate withing 30-60 minutes I had diarrhea...but a sort of solid form of it. It had really weird consistency. The next day I felt better and took it easy. Then today I developed a bad headache that wouldn't go away and my stomach again began to feel poorly. After sleeping I felt much better, but my stomach is still a little sensitive.