This has definitely been one of the biggest struggles for me! I used to eat out a lot, and I am a recovering alcoholic, so I had already been through the whole figure-out-how-to-socialize-without-drinking-thing, but it was the hardest part about getting sober. I think people underestimate how difficult it is to cope socially when you can’t participate in what other folks see as “normal” or “everyday” activities.
I am pretty independent and somewhat of a loner, so it hasn’t bothered me too much staying in most of the time, but there have been some really difficult nights where I came home in tears because everyone was eating pizza and ice cream and having an amazing time and I couldn’t participate. I generally just bring a big bag of snacks and food with me wherever I go, and avoid anything that might involve eating out. One cool thing, though, is that I have started doing a lot of tabletop gaming with folks now, and discovered that it’s a great way to socialize that doesn’t revolve around consuming anything I can’t consume safely!
If you are not feeling emotionally steady, I would highly recommend just staying away from any place that you are not comfortable at. Your friends should understand. Don’t put yourself in harm’s way over social obligation or anything; it’s not worth it.