All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad is His slave and Messenger.
First of all, we ask Allaah The Almighty to remove your anxiety and make a way out of your difficulties (for both of you) and make the marital relationship between you and your husband permanent, as He is the All-Hearer and He answers supplications.
As regards anal intercourse, it is forbidden in Islam and it is not permissible to resort to it in any condition. We have already clarified this in many Fataawa with evidence; for example, you may refer to the following Fataawa: 81499, 83630 and 84137.
Besides, anal intercourse is very harmful. For example, Ibn Al-Qayyim stated some of its disadvantages [and harms] in his book entitled Zaad Al-Ma'aad, and we will mention some of it here for more benefit as he said,
“Allaah has forbidden intercourse in the vagina because of an incidental harm –i.e. menses –so let alone intercourse in the anus which is the place of harm (filth)…also, the anus is not prepared for this act and it is not created for it. Rather, what is prepared for it [sexual intercourse] is the vagina, so those who leave this and opt for the anus are violating both the wisdom of Allaah and His Legislation (Sharee’ah). Besides, anal intercourse is harmful for the man; it is for this reason that the rational doctors and philosophers and others forbid it, as the private parts [of the woman] have the particularity of attracting the congested sperm and thus the man would be comforted by entirely discharging it. On the contrary, having sexual intercourse in the anus does not help in attracting the sperm entirely and the congested sperm does not come out [is not discharged] due to it contravening the natural process.
It harms in another way, which is being subjected to exhausting movements as it contradicts nature (the natural way of having intercourse).
It is a place of filth and feces, which must a man must face (when resorting to anal intercourse) .
It is very harmful for the woman, as it is a strange act that is far removed from the natural disposition of a person and it is very abhorrent….” [End of quote]
Therefore, instead of thinking of this forbidden and harmful matter, one should look for some permissible means, among which is that your husband keeps you as his wife and marries another wife. This is a permissible means by which your husband may attain his objective and this does not affect the love that is between the spouses (you and him). For instance, ‘Aa’ishah was the most beloved wife to the Prophet and despite this, he married other wives and his love for ‘Aa’ishah remained unaffected.
If we presume that your husband separates from you for this reason, then this is not the end of life and Allaah The Almighty will suffice you from His Bounty. Allaah The Almighty Says (what means): {But if they separate [by divorce], Allaah will enrich each [of them] from His abundance. And ever is Allaah Encompassing and Wise.} [Quran 4:130]
Finally, it should be noted that transplanting private parts is forbidden and a decision from the Islamic Fiqh Committee has been issued forbidding it. The decision reads, “Transplanting some parts of the reproductive system which do not transmit the hereditary traits –apart from the private parts –is permissible for an Islamic necessity and provided that this is done according to Islamic requirements and conditions."
For more benefit, please refer to Fataawa 84471 and 82908.
Allaah Knows best.