Answer: Under the Old Covenant in the Bible, a woman was considered "unclean" ceremonially during her monthly menses or period. Intercourse during this time was forbidden.
And if a woman has a discharge (menses or period, the KJV calls it "an issue"), and her discharge in her flesh is blood, she shall be in her impurity (set apart from others) seven days. And whoever touches her shall be unclean until sunset (evening, Leviticus 15:19, HBFV).
Not only were women "unclean" during this time but also the men who had sex with them. Additionally, anyone who touched their discharge was also considered unclean.
And everything that she lies on (when she is apart from her husband) in her impurity (when she is having her period) shall be unclean . . . And whoever touches her bed (it does not matter whether it is her husband or someone else) shall wash his clothes . . .
And if any man (ignorantly) lies (e.g. has intercourse) with her at all, and her impurity (her blood during her period) is on him, he shall be unclean seven days (Leviticus 15:20 - 22, 24).
If you do a little research, you will find there are quite a few contemporary researchers who have found that there are many sound medical reasons for abstaining from intercourse during the time of a woman's menses.
You also asked in your Email about intercourse through the anus (which many Catholics consider sodomy). This activity (between a man and a woman in marriage) is not directly prohibited in the Bible although, for health reasons, it is not wise. What is clearly condemned, however, is this kind of behavior with a person of the same gender. The word of God says he rejects intercourse between men (Leviticus 18:22, see also 20:13, 15 - 16 and Romans 1:24, 26 - 27).