When many different things are going wrong in a short period of time people sometimes say "If it's not one thing, it's another!" This is to say that if "one thing" is not causing a problem, "another" is. Example: "First the car broke down, and now I can't find my keys! If it's not one thing, it's another!" This can also mean that you are busy with too many things to do. Example: "I've got to wash the dishes and do the laundry, and now I hear the baby crying! If it's not one thing, it's another!" When it seems that no matter where you look there is one more thing you need to do or you discover another problem, you might say "If it's not one thing, it's another!"