I used to have the same problem. I avoided sandwiches and rolls from shops. Even tomato could have been cut hours earlier so is a listeria risk. Curry would probably be ok, especially if it's freshly cooked. Same with pasta or pizza depending on the toppings. If it's not freshly cooked and you're a bit worried, you can always nuke it when you get back to the office until it's steaming. Things like roast veges would be ok, I think I had a roast meat sandwich at times. Also fish and chips, or bacon and egg muffins/sandwiches/burgers. There are things that are ok, but ironically they are usually the things that are not so good for you. But remember that you can have extra cholesterol when pg so I took advantage of that LOL!