Hello everyone. I was advised to ask this on here so I thought I will give it a try.
My brother's behavior has drastically changed over the past few weeks.
Some people on the other discussion board even suggested that I should actually use force to make my brother see a psychiatrist (because he refuses to do so, even though I tried to talk him into at least seeing a counselor). I really don’t know if this is the right decision, because I’m afraid of losing my brother’s trust. Therefore, I need someone else opinion before I make any choices. Do you think it's serious enough that he needs to be forced to see a psychiatrist? I will try to describe everything in details.

His change in behavior was sudden but I don’t know what’s precisely wrong with him or how to help him because he will not talk to me, or to anyone else. He’s 17. He was always liked by everyone, he was kind, caring, he had perfect grades, he was very devoted to practicing piano (he’s extremely talented). Then something has changed. He lost interest in everything. As if he’s completely a different person. He seems very depressed, skips college all the time, spends all day in bed, snaps at everyone. What worries me most though, is that he started taking strong sedatives, I don’t even know how he got them in the first place, but when he takes them, he just seems totally unresponsive. I know that he suffers from nightmares. Sometimes I can hear him crying after he wakes up. Still, he refuses to talk to me. He won’t even let me try to help. Another think that I find really strange, is that shortly after his behavior change, he suddenly announced that he’s gay. He just looked at me and said “Your brother is a damn ****** I thought you should know that”. At first, I thought he was joking, but he keeps claiming that he is gay. I don’t really feel comfortable saying this but I guess it’s ok since I’m anonymous here but sometimes, when he wakes up in the middle of the night, he will crawl into my bed and say stuff like “Does it turn you on when we sleep together like this? Do you wanna do it with me?” He doesn’t touch me in a sexual manner though, but after saying that stuff he will just curl up and go to sleep (he won’t back into his own bed though). Of course, I tried to tell him to stop hundreds of times but he won’t listen. After his behavior change he generally became very vulgar, especially when it comes to talking about sex, sometimes I just don’t recognize him. There’s the last thing which really concerned me… His internet history. For the past few weeks he’d been reading horrible sadistic stories. I really mean it, they are just so disgusting, they make me sick. They are all about abuse, torture and rape (only male on male though), and he reads them every day.

Some more information:my brother lives with me. I’m already 19 so I moved out half a year ago. My brother begged me to let him live with me because he said that he doesn’t get along with our father. So I let him, I though it was just going to be a short term thing but he didn’t change his mind. I don’t mind him around, so I’ve never tried to make him live with our parents again. Our parents don’t really care much. so I’m not sure if talking to them won’t make things even worse.

Even today, I tried to talk to him but he completely ignored me, he didn’t even look at me. He just said that he’s skipping tomorrow again so he asked me not to wake him up. I came back really late last nigh and he was already asleep, unfortunately, once again, in my own bed. I decided to sleep in his bed because to me, it just doesn’t feel right to share a bed with him, but he woke up after a few hours and actually sneaked into the bed with me, again. I was too tired to argue with him so I just let it go. As much as I dislike saying this, he was talking about sex again, I know it sounds strange but it’s just as if he’s trying to provoke me to see my reaction. I ignored that behavior and he finally calmed down and fell asleep. I probably wouldn’t see anything wrong with sharing a bed with him, for example if he was just scared because of the nightmares he suffers from, that would be understandable, but it’s the fact that he says all those things to me, idk it’s really illogical to me.

2 people form different discussion boards actually suggested that he might have been abused in a sexual way, and that's the reason for his behavior. Still, I don't know what to think of this, wouldn't he avoid sexual stuff if that would be the case? He, however, actually seems obsessed with sex now (not in a healthy way though, I mean the way he talks to me, and all the rape stories he reads). He was always rather shy when it comes to that stuff, blushing all the time even when he was watching non explicit film scenes, that’s why it shocked me even more.

How am I supposed to help him, when I don’t even know what’s wrong with him and he doesn’t want any help? Do you think that he might have some sort of mental illness? I’m very worried about him. He looks ill, too, he looks like he hadn’t slept in weeks and I think he lost weight because he looks even skinnier than usual..
Please, offer me some advice, I feel completely lost. Should I use force to make him see a psychiatrist? Or do you think he needs more time? How should I act when he sneaks into my bed and says all that stuff?
I'm sorry, I know it's a long read.