Is it permissible to pray and fast while black blood is coming down outside of the time of menstruation, and what can I do to regain Khushu' (devotion/humility) in prayer?

If black blood appears at a time when it could be considered menstruation, then it is menstruation, even if it is outside the usual days, because the custom may change. However, if it appears at a time when it cannot be menstruation, then it is irregular bleeding (istihada), and in that case, the woman is like one who is pure in terms of the obligation to pray and fast, and the permissibility of her husband having intercourse with her.