Progesterone
Progesterone is identical to the hormone the ovary produces after ovulation, and it acts on progesterone receptors to oppose the effect of estrogen on the uterine lining. In menopausal therapy it is given alongside estrogen to protect that lining, and it is also used in cycle-related indications.
It is taken at bedtime, and that timing is deliberate rather than arbitrary: progesterone is metabolised into compounds that act on the brain much as a sedative does, so it reliably causes drowsiness, and taking it at night turns that into an advantage. Dizziness and a hungover, slowed feeling the next morning are possible, so driving or operating machinery deserves caution until the effect is known. Alcohol and other sedating medicines will add to it.
Drowsiness that persists well into the day, severe dizziness, or unexpected vaginal bleeding are reasons to see a doctor rather than adjust things independently.
Reference information, not medical advice. Discuss any change with your doctor.