First,
Second, Chell gave some great advice especially when she said check all of the ingredients. Unfortunately, these foods often masquerade as other things. For example, vegetable protein is often soy protein.
Third, Your post sounds exactly like my problem last year. (I had recently found out that I was allergic to, or intolerant of, soy, dairy, corn, and gluten among other things). I am not going to deny it, it was hard at times, like watching my family eat corn bread (my favorite!) while I couldnt even eat sandwich bread!
Or wanting something to eat, but not wanting to spend an hour or longer cooking something. (I admit it, Im lazy and I HATE cooking lol)
One thing I do is make my own food and bring it with me when I am traveling. Another tip is, get rid of the spices and most things are ok. For instance, no rubs on the turkey, fruit salad made from fresh fruit (or get the canned fruit in water, the syrup ones are all in corn syrup
) Veggies plain work, (although I know its tougher if you like butter on them.) Deserts are a bit harder. There are some mixes by Bobs red mill that are pretty good if you add a bunch more sugar than the directions state. (I absolutely LOVE the muffin recipe on the back of the white rice flour (but add a bit more sugar until the batter tastes good) Enjoy life also makes really good chocolate chips. Be very careful though, as many foods have corn or soy in them. Vanilla extract, for instance, often has corn syrup in it.
I found a lot of snackish type foods at whole foods and trader Joes. Stocking up on these can help deter you from cheating (be warned theyre usually expensive) I went
when I first saw the prices.
Trader Joe has some ok gluten free pasta too. (I like the brown rice spaghetti best plus its cheaper than other places especially when its on sale). However, it tastes weird at first unless you put a ton of sauce on it (homemade not store bought). I made a pasta dish (that I accidentally created one day) and my friends and family could not tell that the pasta was gluten free.
Also have fun experimenting! I discovered a couple of really good recipes by changing things up a bit.
Some simple staples that I use:
Baked chicken and white rice
Pot roast (cut up some potatoes and carrots and stick them in the pot too)
Chili
meat stuff (Im real creative with names lol) my all time favorite new food which is basically just meat (ground turkey or hamburger, left over cut up pot roast, or chicken etc) in crushed tomatoes, noodles and spices. SOOOOO good!
Baked french fries
Fruit salad
If you can have almond milk, that opens up a bunch of possibilities.
For breakfast rice cereal or oatmeal is good
Basically though, health food stores are your friend
Believe me, I know how hard it is. Those four foods are ADDICTING! They are also in almost everything. I havent been able to eat out in a couple of years because I always end up sick from cross-contamination. Ive found that simple homemade meals are best.
Im so sorry you have to go through this especially around holidays that are so food oriented. But, remember, you are not alone.
Now I have to read every food label and be extremely careful eating out otherwise 
), and we got through the holidays by preparing a dish or two that he really loved and could eat and bringing them with us. It still sucked that he couldn't have some of the stuff that looked so good, but he was great about trying to focus on what he could have, and how much he liked that. Thanksgiving is his favorite holiday, and was even when he couldn't have much of the stuff on the table. Having an item or two that's a real treat to you helps a lot, I think.
