Praise be to Allah.
One of the objectives of sharia in marriage is to produce children and perpetuate the human race. Therefore it is not permissible to do anything that will permanently prevent having children, except in cases of necessity.
It is permissible to use means of preventing pregnancy for a limited period, which is what is known as contraception, on condition that it be free of harmful effects.
If you can consult a trustworthy doctor about contraceptive injections, and how appropriate they may be in this case, and how effective they are, that would be a good thing.
It says in a statement of the Islamic Fiqh Council on the topic of spacing pregnancies:
… Secondly: it is prohibited to eliminate the ability to reproduce in both men and women, which is known as sterilisation, unless there is a necessity for doing so, which is to be determined according to the standards set out in Islamic teachings. Thirdly: it is permissible to take temporary measures to control reproduction with the aim of spacing pregnancies or preventing pregnancy for a specific length of time, if there is a genuine need to do so, according to whatever the couple decide, on the basis of mutual consultation and agreement between themselves, on condition that this does not result in any harm, and that the method used is Islamically acceptable and will not cause any harm to an existing pregnancy. End quote from Majallat al-Majma‘ (issue no. 4, vol, 1, p. 73).
If qualified doctors determined that giving birth will harm the woman, or exacerbate her sickness, or there is the fear that pregnancy or birth will lead to the woman’s death, then it is permissible to abort/prevent pregnancy, with the husband’sconsent.
Shaykh Ibn Baaz (may Allah have mercy on him) was asked about a woman who had given birth to 10 children, and would be harmed by any further pregnancy, so she wanted to have her tubes tied.
He replied: There is nothing wrong with the operation mentioned, if the doctors have determined that producing more children will harm her, so long as her husband gives his permission for that.
End quote from Fataawa al-Mar’ah al-Muslimah, 5/978.
He was also asked: What is the ruling on hysterectomy for sterilisation purposes, that is to prevent pregnancy for medical reasons now and in the future, because ??? medical and scientific ???
He replied: If there is a necessity for that, then there is nothing wrong with it, otherwise what one must do is refrain from that, because the Lawgiver encourages having a lot of children so as to increase the numbers of the um mah. But if there is the risk of harm, then there is nothing wrong with it, just as it is permissible to use contraceptive methods temporarily for a legitimate reason.
End quote from Fataawa ash-Shaykh Ibn Baaz (9/434)
Shaykh Ibn Jibreen (may Allah have mercy on him) said: It is not permissible to have medical treatment to prevent or end pregnancy except in cases of necessity, if doctors have determined that giving birth will cause irjaaq, or will exacerbate sickness, or there is the fear that pregnancy and giving birth will lead to the woman’s death.
However in that case it is essential to have the husband’s consent and agreement to preventing or ending pregnancy, then when that reason is no longer applicable, the woman should go back to her previous state.
End quote from Fataawa al-Mar’ah al-Muslimah (2/977)