Menstruation is read as cycles, renewal and release — the end of one phase and the start of the next. Bleeding unexpectedly in front of others points to fear of embarrassment or of something private being seen. A period arriving when it should not is linked to worry about timing and plans. For men, dreaming of it is read as contact with cycles and feelings they rarely voice. It is a symbol of change and natural rhythm, not a sign about the body.
Has this come up in your dreams before? What was going on in your life then?
My Cosmic Code has a private dream journal. Write a dream down and the app picks out the symbols in it, shows what dream books say about them and, over time, which words recur across your entries. The journal is stored on your device only.