I had gone back and forth about having DID for years since when I first learned about it. I had come to the conclusion that I wasn't DID a number of years ago, after no therapist would ever confirm the DID or the possibility I might have alters. However, I have always known that I'm dissociative, and that I have "other states" take over me where I feel as though I'm watching myself and as though I'm not "me." I never could figure out what that was. When my previous T begin seeing some of these "switches", where I felt different (extremely different), she diagnosed me as DID. I followed along, and tried my best to accept the diagnosis, since she seemed very sure of herself. That's when I found this forum for support, and my exploration of myself and my condition really began.
Some of the experiences described by people on this site I shared, but a fair number I didn't. However much I tried getting to know my "parts" and learn more about them (their ages, their possible names, their likes/dislikes, really anything about them), I came up empty handed. These parts of me didn't seem to have a strong sense of identity that others on here described. All the parts of me felt like me, they just felt different.
Here is analogy:
Imagine that every human being is like a picture. I'm going to take the idea of a lion, since I really like lions. For a non-dissociative person, let's say their lion picture, or sense of themselves, is more or less wholly intact. There may feel like there might be pieces missing, or some parts of the picture are vague or fuzzy, but one whole picture for the most part. Even non-dissociative people have different parts, or ego states, so let's say sometimes they feel like the head, sometimes the tail, etc etc but their overall sense of being the lion never wavers. For someone who is DID, let's make the picture a puzzle, with separate pieces, and in addition to that, let's make the picture have lots of different animals. So each puzzle piece (or "part") has his or her own animal identity. There is a lion, and a cat, and a dog, and a rhinoceros, and they all feel and know strongly who they are. For me, well, I'm somewhere in between. I'm a picture of one big lion (like a non-dissociative person) that has been divided up into puzzle pieces (like a DID person). If you were to take any one piece, they would still identify as the lion, since they are literally one part of the larger lion picture. They don't feel like their own independent animal. Their identity is wrapped up in the larger lion. They don't feel like their own animal, nor do they want to be their own animal. If you were to ask each piece what animal they are, they would say, "I am a lion." So this is my experience, if it makes sense.
Whenever I have tried to "get to know" any part of me, they would get confused or flustered by my questions. Whenever I tried "naming" the different parts of me, these parts got upset, because they all just wanted to be thought of as the main name that we all share. The difference between myself and someone with DID is that I don't know which part I am. I consist of many parts. But the difference between me and a "normal," non-dissociative person is that my parts are fairly distinct, and rather than me feeling in control of when and where I become which part, they seem to take me over, most often at times when I am triggered.
When I get overwhelmed, a very young feeling, self-hating part comes out. This part tends to cry and apologize for things, even when they are not my fault, and hates herself and wishes she weren't alive. Everything overwhelms this part. I normally don't feel like this, but I can get triggered into this part. However, ask this part how old she feels, or what is her favorite color, and she doesn't understand. She doesn't have a strong sense of herself. She doesn't feel like a certain age, she doesn't feel like a boy or a girl, she doesn't have a favorite animal, all she knows is that she hates herself and feels overwhelmed. And when I am in that state, I feel like that is me. It doesn't feel like another part but rather that I become that part. Same with my angry, people-hating part of me. This part has no likes or dislikes, no personal preferences besides thinking that the world is a really messed up place, that all people do is hurt, that no one can be trusted, and that she is overwhelmed with anger almost all the time. My "main" part of me doesn't feel this way (and in fact, I tend to be overly trusting and not listen to my instincts about people). When this angry part is triggered, I feel that this part is me. I become the angry, pissed off, jaded part. It's not a separate part of me, or like that's another person that is not me. Instead, I actually become her. Rather than me being one part of many, I feel like I am many parts. It's just these parts feel separate, and I don't have any control over which part I am at any given time.
I have never felt that I have other people who live inside my head, or who share my body. I have never lost time. Although I have heard people talking to me in my head, I have never thought of these voices or thoughts as anything other than myself. I know my experiences are very similar to some people on here who are extremely co-conscious, and that's why it's been such a difficult process of figuring out what's going on with me. However, with DID, the shoe just never seemed to fit. I didn't fight the idea because I was resisting the truth about myself, I fought the idea because I tried it on for size, and it just didn't feel right. I gave it a good and valiant shot, it just didn't match my experience.
Then, in someone's thread (I can't remember whose), people were talking about the idea of dissociated ego states. I had never heard of this idea before. I always figured you either had "normal" ego states (in the non-dissociative person), or you had alters (in the case of DID). I didn't realize that ego-states could have dissociative elements without being alters. They can carry "feelings" or "mood states." When I thought about that, I thought, "THAT'S IT! THAT'S EXACTLY WHAT I EXPERIENCE!" These states can take me over, and I can even have major depersonalization or derealization accompany them, but they are all still PART OF ME! They are not their own distinct parts with their own personalities and identities! Finally, something that seemed to match what I am experiencing!
I am still in the process of finding out more about this idea of dissociated ego states, but so far, it seems to really fit my experience, and this thrills me. I ordered a memoir of someone who has experienced dissociated ego states, and I will update you all as soon as I receive and read the book. Also, if anyone has any articles, links, or addition info about ego states (and especially dissociated ego states), that would be very much welcomed!

That, in a nutshell, has been how I arrived at the conclusion that I don't have DID, but something quite similar.