Small circles or blisters in a line caused by nails or screws, indicating that the sheet may be separating from the beam (beam) above it. You didn't find any but are you still worried? Take a tape measure and the alcohol level. Measure the height at which the ceiling meets the wall. Then measure the height in the center of the room.
A difference of 12 mm or more could indicate that something has come loose. Using an alcohol leveler on the ceiling areas will confirm any unevenness in the ceiling. The lines that cross the ceiling must be straight. Once a month, pick up a level and place it at key points against the ceiling.
If the level bubble is not in the center, it is an indication that the ceiling is sunken. If you know the signs, you can request a roof damage repair to prevent serious damage to your home and, more importantly, serious injuries to you and your family. Unless you're in the habit of shooting water guns in the air, there shouldn't be ANY water on the ceiling.