Should I pray now and perform ghusl before it, or am I considered to be menstruating, knowing that I feel menstrual pain but do not see blood, and 37 days have passed since the expected time of menstruation, and some spots of blood appeared yesterday?

The minimum duration for menstruation to be considered valid is one day and one night, and this is the view of the majority of scholars. As long as the spotting of blood does not continue for a full day and night, it is not considered menstruation, and prayer remains obligatory. These spots are impure, and one must cleanse oneself from them (perform istinja (definition)') and they only nullify wudu' and do not necessitate ghusl (definition). The Fiqh Encyclopedia mentions that the minimum duration of menstruation is one day and one night according to the Shafi'is and Hanbalis, and its maximum is fifteen days. The Hanafis hold that its minimum is three days and nights, and anything less than that is considered istihada (non-menstrual bleeding). As for the Malikis, they believe there is no specific time limit for the minimum duration of menstruation. Based on this, the spots of blood that did not continue are not considered menstruation according to the majority opinion.