Is it normal i think i have a personality disorder

There are times where people tell me I've done something that's typically out of character of me to do, and not remember it at all. For example a day ago I learned that while talking to my younger sister I was being extremely mean to her, yelling at her and telling her to shut up. She told me this and I honestly didn't remember it at all, and didn't believe her.

I also get mood swings where one day I'll be completely fine and love life, but the next day I'll be depressed for no reason and feel suicidal.

I also have another voice in my head who I talk to, who might be the one that I switch to and that's why I can't remember doing some things. He's very mean and violent, he likes to play games with me and joke about hurting or killing people. He is very negative, for example when I had an argument with my mum he was saying really mean things about her and told me to kill her.

Despite that I think he understands that if I (or him) actually kills or assaults someone the body is going to jail, I was talking to him about it and he told me he wouldn't kill anyone because "being in prison isn't fun."

He still talks about hurting people but if I get angry at him he stops and tries to laugh it off or make it as a joke. He has actually been nice though sometimes, he's never made any threats to me at all, it's always just other people and he has given me good advice on occasion.

He also does things for me, like gives me motivation or if I can't do something (like get up in the morning) he'll call me a lazy fuck and take over to actually get me out of bed but it's different from the times where I don't remember doing something cause I don't mind if he takes over to help me, and it's like I'm still there but watching and basically being able to watch but it's not actually myself moving my body, if that makes any sense? It's usually only a very short time, like 30 seconds then he'll let go and let me get on with doing my own thing.

He can be a bit rude to me if he's in a bad mood, he'll tell me to fuck off if I try to talk to him or wont answer me. Right now he called me stupid for writing this lol.

None of my family/friends or anyone I know in real life know about him, and I've never spoken to a doctor or psychologist. He tells me to never tell anyone especially any doctors because he's scared if they give me medicine that he would leave/I wouldn't talk to him anymore.

Generally though I don't want to get rid of him, he's been with me for almost all my life and it's like he's apart of me, which well I guess he is haha.

So the reason I wrote this is because I want to know if I do have some sort of illness/disorder and what do you think? Also feel free to ask me questions, or ask him something but it's up to him if he wants to answer or not, and if you do wanna ask something he is rude so if he swears at you it's not me it's him lol