In your situation I think I'd push for a biopsy as soon as possible. Try to get a last minute cancellation if you can, or push the GP for an urgent referral.
I'd stay eating as much gluten as you can - remember you're almost there and as soon as you've had the biopsy you can go GF.
You could also try getting an appt with the gastro to request a CD diagnosis without biopsy because of your Ttg results and history. They might be willing to do that in your case.
Hang in there though - you're doing all the right things and am sure your persistence will pay off in the end. Good luck.