Each woman's body contains hundreds of different kinds of hormones, and three play a major part during the menstrual cycle. The levels of testosterone, oestrogen and progesterone go up and down throughout your cycle, and this has a major effect on how your body functions.
In the week before your period, the level of progesterone in your body rises. Progesterone has a sedating effect, which may make you feel listless and fatigued.
During this time in your cycle, oestrogen levels decrease. Declining oestrogen levels lead to bursts of another hormone called noradrenaline, which can keep you from reaching REM sleep.
Testosterone levels also decline leading up to your period, lowering energy and endurance.
At this point in your cycle, you are more sensitive to sounds, smells, and pain, which may have an effect on your sleep patterns.
Try using a fan or sound machine during the night to block out distracting sounds. Even though you're tired, try to avoid caffeine; it can make premenstrual symptoms worse.