I also have to family history, and symptoms, but inconclusive blood tests.
Do some research on the internet about false-negatives results, clinical trials (if you stop eating it and get better, there's your answer.)
It's too bad that he's not more supportive on his own, but work at it. Prove it to him! And I say don't wait to go gluten-free. Everyday you keep eating you're losing a day towards your full recovery!