You're twice as likely to experience insomnia right before and during your period. Although researchers are uncertain about exactly why this happens, there are studies that have identified potential reasons...
☾ A change in hormone levels may make it more difficult to fall asleep, while also increasing sleep disruptions. Multiple studies have shown that sleep worsens during the late-luteal phase (when PMS begins) in comparison to other phases of our menstrual cycle
☾ Progesterone (which increases after ovulation, until the late-luteal phase) increases body temperature which can result in broken sleep. Some research has also found altered levels of melatonin during this time, disrupting our circadian rhythm
☾ Studies have found some of us have less rapid eye movement (REM) sleep during the late-luteal phase. REM sleep involves heightened levels of brain activity and is associated with vivid dreaming
Take note of whether you notice any sleep disruptions during this time of your cycle. The late-luteal phase is a good time to start slowing down, allowing your body to have some extra rest.
Source: sleepfoundation.org