What is the ruling on prayer and intercourse during the last four days when light brown spotting occurs after the cessation of menstrual bleeding, which used to last 4-5 days after IUD insertion, knowing that before the IUD, my period was 5-7 days, and sometimes the cotton swab is completely clean after checking for traces on the day of increased menstrual bleeding, and sometimes it is not?

What a woman sees of yellowish or brownish discharge during her menstrual period is considered menstruation, based on the statement of Marjanah, the freed slave of 'Aishah: "Women used to send to 'Aishah small boxes containing cotton pads on which there was yellowish discharge, and she would say, 'Do not hasten until you see the white discharge.'" And what she sees after purification is not considered menstruation, and your ruling is that of pure women. Thus, prayer becomes obligatory for you, and it is permissible for your husband to have intercourse with you. The dryness by which a woman becomes pure is when a tissue placed in the private part comes out uncolored by blood, brownish, or yellowish discharge.