Hello there. If you want a loaf that stays fresh without chemical preservatives, you should look for naturally fermented sourdough bread. During the fermentation process, the wild yeast and lactic acid bacteria produce natural organic acids that act as natural preservatives, inhibiting mold growth and helping the bread retain its moisture much longer than commercial white bread.
When you are at the market, check the ingredient list to ensure it only contains flour, water, salt, and starter. Storing it in a paper bag or a bread box will also help maintain the texture for your sandwiches throughout the week.