Welcome to our community.
I now need to go in for an Endoscopy/Colonoscopy and D2 Biopsy on 20th March - not sure why both?
To the question in the quote, there are other things that can cause symptoms similar to celiac disease, and celiac disease is associated with other issues, including colon cancer. Even if you do have celiac disease, it is important to have the colonoscopy to be sure that you do not have other issues as well.
As to the warfarin question, nobody here knows your specifics, and even if we did, none of us are qualified to give a medical opinion. Talk with your doctor about this, make sure they know about your concerns, and then TAKE THEIR ADVICE.