Here are some old threads on navigating boozy situations as a sober person
My experience of going to things with people I don’t know well is that they generally don’t ask if when I say I don’t drink. And if they do, or if i want to offer an explanation, I just make a joke of it… I used to drink, I don’t any more, it’s best that way 
kind of thing.
It is totally normal to have anxiety over this by the way. At some point though it clicked for me that no one cares about my drinking (or not) as much as I do. As long as you’re not sitting here lecturing everyone on their behaviour, why would they?