ANSWER:
Anal sex is one of the major sins in Islam and Allah has cursed those who do it! If he forces her to do this, she must refuse and resist and if needed, threaten him to expose him to his parents and your relatives and that you will obtain medical records to prove that he has forced himself on you like this! You must tell him that Allah curses those who do that and if he still insists, tell him that you will ask for divorce if he doesn’t stop!