They are also not unique to any particular disorder. We do see changes in the kinds of nightmares that children have according to their age. That is, at some ages monsters are important, and at another age other sorts of things such as death may be important. So we do see those patterns, but there is nothing characteristic of sexual abuse in and of itself with nightmares.
Stomach aches occur with many kinds of stress disorders.
Needing a night light on is a frequent occurrence with many children, including many nonsexually abused children. Wetting bed sheets is also not necessarily a usual symptom of abuse. There can be, again, many causes. A child could be angry at being separated from a parent, being in the middle of a parental conflict, going through a divorce. There are many, many stresses that a child can be subjected to in a case of this sort.