@PenfoldAPD - When I was diagnosed, I made a pact with MrB that I would never decline an invitation due to my diabetes, and I am proud to say that so far I have kept that pledge.
During MrB's career he has done many things and owned many businesses, including rather a smart Bistro/Restaurant, where he used his time as owner to really up his game in the cooking stakes (He owned the place, wasn't it's cook). You can imagine how my diagnosis went down at home!? Lead balloons had nothing on it.
Anyway, like everyone else I've had my moments where I've been a bit fed up of it all, but I've come to realise these get-togethers include food, but really the joy in is communing with friends and sharing good times.
I can honestly say I have never gone out; whether to someone's home, or to a commercial establishment, and found absolutely nothing I could eat, although sometimes I have eaten modest portions or ignored some things on my plate. Aside from occasionally asking for extra veg, instead of rice or whatever, I don't ask for subs.
When friends commented I wasn't eating pasta or rice or whatever, I explained I'd had some bloods done and the results suggested I wasn't handling some foods to well, so I'd given them up. I have only really used the D word with a few folks, although more recently I'm a bit more free on that as more folks around me seem to be being diagnosed.
It sounds to me like you're clinging for dear life onto the "old life", rather than embracing the new one. I'd urge you to take that step forward if you can. It makes life simpler and much more enjoyable.
Oh, and on the less great days, I just sulk a bit until I give myself a bit of a talking to.