Mom is Drug Addicted, How can I stop her from hurting me?

This happened almost two years ago when I was 15 years old then and I used to live with My Mom and her boyfriend, But Mom's boyfriend was not a good Guy, he used to sell & take drugs and he made My Mom addicted of the drugs too, Mom spent her all savings on drugs and her boyfriend started taking advantage of her situation, Once When Mom didn't have money and she tried to borrow Money and drugs from him, he put a condition in front her, He asked Mom to fuck my butthole by a strap-on in front him and his friends, At first Mom refused but after some days she told me about this, I got very shocked and upset hearing this from Mom, but she said that she needs Money to meet the house expenses and there is no other way to borrow money ( she had already sold valuable Assets), she forced me by saying it is just for One time,
I was 15 years old and I had to agree, then he bought a strap-on for Mom and she fucked my butthole in front him and his friends and they made a video of this too to sell it, I felt horrible pain in my butthole and I felt too much insulted and humiliated but I had to tolerate it, after this he gave Money and drugs to Mom and Since then it has happened 4-5 times, it hurt my butthole badly, But Still Sometimes Mom do it to get drugs and Money from him because she can't live without drugs, He and his friends are involved in drugs business and they also sell these sort of videos to make more Money, Sometimes I feel extreme Pain there and it can damage my butthole seriously, What shall I do to stop Mom?
I am also scared of Mom's boyfriend and his friends.
Mom is Drug Addicted, How can I stop her from hurting me?
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