Everyone is telling me I have to go as it’s our yearly tradition
I have someone in my family who has this issue and they do sometimes go to things where they can't eat anything because they want to join in the event and see those people all in one go and understand that for whatever reason moving the event isn't a viable solution. It's nice to sometimes see people enjoying what they enjoy even if you can't.
However, if it was me, I wouldn't be liking the attitude of your actual family to this, so I might refuse to go on principle to make this point very firmly to them. It doesn't bode well, what else would they not budge for? People can be VERY funny around food, and traditions, and personally I try to avoid those sorts of people. My family and friends aren't like this at all which means the planning for going out is very inclusive of medical conditions, and other needs that apply to the venue. I did have some ex-in-laws who were though. Urgh.
One alternative is to ask the venue if they mind you bringing your own meal (such as a GF pasta salad or something that will travel well) and buy drinks and maybe dessert if they have the right thing. Only if you WANT to do that to join in the bonhomie. Or just eat first and buy drinks and nibble on chips (but, would they be cooked separately - how sensitive are you seeming to be to cross-contamination?).
6 weeks of eating gluten again is too little to get a definitive coeliac diagnosis and it's understandable that you don't want to reintroduce it. They used to say at least 10 weeks of eating a normal amount of it, and even that isn't enough for some people; it's know about 20% of people (that may not be the latest estimate, but in that ballpark) who do have coeliac disease don't get a definitive diagnosis that way, ever. 20 years ago there was also no such diagnosis as "non-coeliac gluten intolerance" and you weren't allowed to join Coeliac UK without a coeliac diagnosis, but now you can. Also you can join if you avoid gluten for other reasons such as having another autoimmune disease that responds to a gluten free diet. Times have moved on. (I humbly suggest that a good proportion (all?) of the now-diagnosed "non-coeliac gluten intolerant" folk will be shown to actually be coeliac, down the line.)
So I'd recommend joining Coeliac UK to get support, the directories, etc. There will be a lot of people navigating selfish families at this time of year who can help you with practicalities and how you feel about it. And here's to eating what works for you to stay well.
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