What is the thing that controls me?

Hello I'm about to write down some things that happend while I was being controlled by my alter. This has all been discribed to me by a very dear friend. A friend who rescued me from suicide and is helping me now to control the thing inside of me.
No I've not been diagnosed with MPD/DID (yet) because my psychologist wants to do some more research first, but I know he exist and he knows it too. I always had converstations in my mind. And I sometimes blacked out to discover later that I did something terrible. Shouting at people, hurting my parents or my brother, Disregarding the rules of school or work. I did allot of stuff without me knowing it. But I never thought that it could get this serious and it scares me allot. So please read my story and tell me what you guys and girls think I should do. because I don't know anymore.

First of all I was at my friends place when it all started to take shape. we were talking about my past and what I did before we met. It was quite a long talk and she knew that this wasn't going to be finished in one night. So after about a year of intensive converstations with her, she thought that she was talking to multiple persons. She explained to me that what I wrote and what I said were sometimes completely different and when she talked to me she sometimes sensed that my whole appearance, voice and attitude would change drasticly. After hearing al that she showed me all my vent letters and poems I gave her. She underlined everything that was not told by me. Sometimes whole pages would contain discussions, arguments and converstations with an unkown person that resides within my mind.

After hearing and reading all that I started to think even more than I already did.I didn't sleep either because of the constant conversations in my head. I never slept allot but this was becoming a real problem. She told me to see a docter. I did and I was sent to Buro3o. This institution works with children, teens and young adults. When I got there for the first time I was really nervous and couldn't speak at all. I shut down completely. There was a conversation none the less. But not with me. The second time the psychologist told me about wat we talked about last time and if I wanted to continue. I told her right away that I did not tell her that. She started to suspect things and began her research. I asked my friend to come along the next time and she told the psychologist all that she knew about me and even showed her the letters and poems. This brings us up to date regarding my weekly visits to the psychologist so I still don't know what she is thinking. Quite frustrating really.

Now to the question stated in the title. What is the thing that controls me? I still don't know. My friend started to call him Ukkie. Because of his childish behaviour but that can't be all there is. I lost control last night when I was with her. I started very violently. I had a bad day and I really needed to cry. But when I did I also started to breath heavely and I couldn't control my arms anymore. I started shaking all over and that's when it happend for the first time. The first time I tried to fight him for control. Normaly he would take over just like that. No shaking, no nothing. But this time I didn't want him to take control I sensed him taking it but I couldn't hold on for long. When I was back my friend told me what happened when I was away. They talked about allot of things that involve death and suicide. She never gave the full story because she was afraid I would do something stupid. But that was the first time that I fought back. It hurts. It really hurts allot, physical and mental. But she did discribe this. When we fought for control it was violently but after the fight he was completely calm and relaxed, it must have looked strange. After he was done I came back in the state that I left. In panic, in pain and heavely breathing. I also started crying again. That feeling was so bad that I never wnat to fight it again. But I can't let him take control over me because I know bad things will happen if he does.

So if anybody knows what this could be. Please tell me. Because I don't think that this psychologist is going to tell me any time soon and my friend doesn't know either.