My doctor told me that you need to be on gluten at least once a day for 6 weeks for the blood test to work. I did that, and had similarly inconclusive results... and the doctor said even on gluten for 6 weeks, it could be not enough time to see a reaction (this is just for a blood panel, not an endoscopy).
So in my experience, you might not have been on gluten enough for the blood tests to work. I have read some forums that suggest 3 months. And for the endoscopy, it depends how many samples they take, from how many different places etc.