Which statement from a patient suggests mittelschmerz as a possible diagnosis?

The statement indicating that the patient had sharp belly pain but it seems to be going away now aligns with the characteristics of mittelschmerz, which is a term used to describe mid-cycle pain associated with ovulation. This type of pain is typically unilateral (on one side of the abdomen) and can be acute or sharp, but it often resolves relatively quickly, which fits with the patient's description of the pain diminishing.

In contrast, the other statements belong to different clinical presentations that might suggest other conditions. A constant ache in the lower abdomen might indicate an ongoing issue or a different type of gastrointestinal or gynecological condition, while sudden, severe pain could suggest an acute abdominal emergency such as an appendicitis or ruptured cyst. The mention of not eating or drinking does not directly relate to mittelschmerz and instead raises concerns about dehydration or another underlying issue. Thus, the nature of the pain in the accepted answer provides a clear indication of possible mittelschmerz as a transient and resolving mid-abdominal pain.