If you do have DID, you've had it all this time since childhood. It would be a good idea to look up the symptoms of DID, DDNOS, and CPTSD to compare those to what you are experiencing. All these are on the spectrum of dissociative disorders. Educate yourself as much as possible on the basics of these disorders, because it's easy to get mixed information from individual experiences. Everyone is very different, even within these diagnoses.
The reality of DID didn't crash in on my consciousness until age 36. I was in therapy doing EMDR, which was bringing up more traumatic memories than I could handle, and one of my alters started talking to me. He told me I needed to listen to him because these memories were too much for me. He also said he would stop my next therapy session if needed to keep me from being overwhelmed. Honestly, looking back I can't believe I denied so much of what was going on in my head and my life. Of course, that was my job--to look normal, believe I'm normal, and maintain normal life.
As far back as I can possibly remember I have talked to myself constantly when alone, in different voices, answering questions, laughing at my jokes, and referring to myself as we, both privately and in my thoughts. I have also always had internal voices. These voices remark on what I'm doing and have their own ideas about things. I was seriously surprised to discover other people don't have voices in their head. For me it was just like background noise I was used to. And with the talking to myself, I just thought I was really quirky. Realizing the voices we're talking TO ME was like listening to the radio and realizing the announcer is discussing what you are doing and giving instructions
It was also a leap to realize These were not figments of my imagination, but persons in their own right, with needs and motives and memories different from mine (they remember things I have amnesia about). There was a huge amount of fear, and still is sometimes, in learning about them and getting to know them because it means facing a lot of things about my life that were unbearable. I am who I am because I don't remember the abuse--that's why I seem so normal to most people. They are who they are because for some of them the abuse is ALL they remember.
I remember switching, especially in my twenties, quite dramatically. From day to day I would dress and act differently. (I didn't have amnesia for most of this. Others would.) I was familiar with these mindsets, as I called them, and recognized them when I "met" them later in life. I already knew some of their names. I knew that I would "click into" these different "mindsets" and watch myself behave in ways extremely uncharacteristic of me and be unable to stop myself.