I just have a quick question of covering your hair during niddah days (sleeping). Where does this idea come from and is it strongly kept today?
If you do not cover your hair at home during the time that you are not niddah, you would not have to cover your hair even while you are niddah. However, covring the hair is a worthy practice.
Shulchan Aruch rules that a husband may not see the “covered areas” of his wife while she is a niddah. This would be the reason why some married woman are particular to cover their hair when they are niddah, so that their husbands will not see it. However, Iggros Moshe (Yoreh De’ah 2:75) rules that one may be lenient in this matter — if a woman does not cover her hair at home in other times, the husband will not be induced to improper thoughts by seeing her hair during the time she is niddah. He nonetheless writes that it is worthy to be stringent. Some quote Rav Elyashiv as being stringent on this matter, and Rav Shlomo Zalman Auerbach as having been lenient (Mareh Cohen).