月经周期通常是28天左右，但正常范围可以在21到35天之间。如果你的月经周期突然缩短到半个月一次，这可能表明存在一些健康问题。以下是一些可能导致这种情况的原因：

menstruation irregularity can be caused by various factors, including hormonal imbalances, stress, excessive weight loss or gain, and certain medical conditions such as polycystic ovary syndrome (PCOS) 🩸. It's important to consult a healthcare professional for a proper diagnosis and treatment plan 💊. They may recommend lifestyle changes, medication, or further testing to determine the underlying cause of your irregular periods 🧑‍⚕️.

如果你遇到这种情况，请不要慌张，及时就医是关键。希望你早日恢复健康！🌟