A minor must get parental permission to have sex. Parents have the right to press statutory rape charges against an adult for having sex with their child. Look up "statutory rape"… You don't have a legal right to have sex without your parents permission until you are over 18. That is the law.
I have a friend whose son was dating a girl, and he went to prison for statutory rape. So now he has a criminal record and must register as a sex offender. Tommy (not his real name) was 19 and his girlfriend was 15. They were in love. Her parents were terrified that she was going to get PG out of wedlock and forbade her from seeing him. They told him to stay away from their daughter. Being in love, they continued to see each other and got caught. So the parents pressed statutory rape charges and he went to prison.
It is very dangerous for someone your age to get involved with a man. Likes attract likes. If your boyfriend is sharing an apartment with someone who would do something like that to you, he must have been attracted to that guys energy for some reason, and he must have some violent tendencies too. It sounds like the kind of thing a pimp, or a gang of pimps would do. The next thing you know, they could take you 300 miles down the road to another city, put you out of the car, and tell you to earn your keep.
Women come up missing all the time. If he would do that to you, and get away with it, what is to prevent him from doing even worse things to someone else, or to you if you keep coming back for more abuse. I would recommend that you tell your parents and call the police. I would recommend staying far far away from both of these men. Where was your boyfriend when it happened? Could he have been in the closet watching?
Do not threaten them, or they will get scared, and think they have to get rid of you and shut you up somehow. I would just disappear from their lives. Do they know where you live? There are safe houses when women can go when they have been abused. The police can put you in one, if you will go to them. Since this has happened to you, then you are in danger. You need to protect yourself. ASAP. Because there is always more to come from people like that. They will not stop unless/until they are held accountable.