What Could Causes Continuous Vomiting?

Last night, I only ate a bagel at 6 pm and was very hungry so i ate a granola bar around 11 pm. (my boyfriend who I was with also ate one at the same time). About an hour or an hour and a half later, I felt really sick, and I threw up (A LOT). I never throw up.The last time I threw up when when I had a bad reaction from my meds for strep back in september and before that I hadn't thrown up in 10 years . The last time I really was sick from an illness, I was 8 or 9. Last night, half hour it happened. 12 :30 threw up, felt really shocked and weirded out, then I felt fine and all better. 1:00 am same thing-threw up, felt weirded out and bad, then felt fine. and thta continued two more times until 3 or 4 in the morning. I woke up this morning and was pretty ok, I ate waffles and drank soda and I didn't throw up but I did wake up with a bad headache and feel heavy. What could be wrong?