Even the best of home made bread is only good for a couple of days. It's not like store bread and doesn't keep for very long unless frozen. That's why, for the past 3,000+ years, people have shopped at their bakery on a daily basis, and day-old bread was sold for a few pennies on the dollar.
But in any case, try substituting milk for about half of the water your recipe calls for. It will give you a softer "crumb" (interior texture) that you are probably looking for even the following day.
Oh, and when I store my bread, it seems to do best when kept in a paper bag. Plastic just makes the crust soggy and mold develops more quickly.
"Food is our common ground, a universal experience." - James Beard