@fBoyle-- I don't mean to scare you but my sister was diagnosed with Crohn's disease recently and she had the same symptoms. You should see a specialist about this. You may have to go through many more tests, but it's important to know the cause.
Crohn's disease is a type of immune system disorder that causes inflammation in the bowels. It can also affect the stomach. Bloating and diarrhea are symptoms. The inflammation basically prevents the intestines from functioning normally.