“Why am I such a light sleeper?”

Deep sleep occurs more in younger healthy people who have a good exercise and dietary program. Deep (N3) sleep occurs mainly in the first 3 hours of a normal sleeper. Multiple hormones, like growth hormones, are secreted during this sleep phase. Sleep-deprived patients have less deep sleep so getting 7-7.5 hrs of sleep routinely helps increase deep sleep. There are several medications that decrease deep sleep like benzodiazepines and OTC sleep meds that contain Benadryl and others that tend to increase deep sleep like Trazodone.

There are a few factors. Naturally, women have built-in "great mommy techniques," one of which is sleeping lightly. There are other factors such as stress and lights on. I would need more information in order to give a more educated answer, however, I would recommend meditation and lights out when sleeping should help.