If fleas are biting you at night time or while you sleep, then you most likely have adult fleas in your bedding and linens on your bed and in your sleeping area.
In order to get rid of the fleas and any flea eggs and flea larva that are on your bed sheets, wash them in very hot water with bleach in order to kill and remove them.
Is also a good idea to spread a flea insecticide powder such as diatomaceous earth in the carpeting around the area where you are being bitten. This will kill all stages of the flea life cycle that it comes in contact with.
Finally, make sure that any cats or dogs in your home are treated with flea medicine such as Frontline, because pets in the household are the number one reason why people get flea infestations.