I had a similar problem that I went through for two years. The first doctor thought it was my appendix, but all tests were negative. I was bounced from doctor to doctor and had thousands of dollars worth of tests, all negative. I ended up spending an entire day in the ER having numerous tests, again they said all were negative. Needless to say, I lost it completely. Immediately after leaving the ER, I saw a general surgeon who gathered and reviewed all the tests I had gone through to see if something was missed (it wasn't), so he did an exploratory and in the process, took out my appendix. Turned out, the appendix was full of ulcers - when they flared up, I had symptoms, when they were not flared up, I was fine.