Self testing for dairy intolerance

In January 2012, I started having digestive trouble: bloating, cramping, gas, diarrhea, and weight gain. I ignored it until March that year when I sought out a doctor. The following month, by accident, more than anything, I found I had a rare form of ovarian cancer, and I placed the digestive issues on the back burner. It was not until I had recovered from chemotherapy that I felt I had the energy to tackle the digestive issues. Since all tests came back negative, the problem must be food sensitivity, and I went on the low FODMAP diet to attempt to discover what the problem foods were.