What Causes Bloating Of Abdomen And Vomiting Along With Headaches?

Over the past month I (66 yr. old female) have had at least 6 episodes of sudden projectile vomiting with no nausea beforehand. My upper stomach begins feeling bloated, much like a balloon filling, and the pressure becomes too much. Within a few seconds I vomit violently. Headaches usually occur immediately afterward and subside within a few minutes. Diet doesn't seem to be a factor. Yesterday, the latest occurrence, I ate oatmeal with skim milk, raisins and a few pecans, for breakfast. A couple of hours later I had a bagel with oleo; vomiting commenced about 1 hr. later. Once the episode is over I feel fine. What is wrong with me?