I think I don't have DID, but I guess I'd like to be sure, because while I have only noticed a few potential signs, they seem to be rather strong ones. So, I guess I'll list them and then you guys can tell me what you think. Also, apologies in advance if I say anything that might sound rude or something; I am both trying to convince myself I do and don't have it so some things might sound a little strange.
I guess the strongest one is that I'm pretty sure I have at least one alter... Here's the story about her. I first remember her showing up when I was around 9 or 10, when she tried to beat up my (then) best friend at a sleepover and got laughed off. Cut to 5 or 6 years down the road, she got thoroughly pissed off at my (again, then) boyfriend for some slight or another, I have no idea what, and ranted at him over IM for a good long time. Actually I do kind of remember part of that, but not most, and definitely not what she said, or even really what he said, but afterwards she vanished suddenly and we both agreed that I had sounded like a completely different person there, but I think he was still sore about it... I made a snap decision not to save that conversation and have since regretted it, but maybe that's for the best... Anyways, another 5ish years later, she came out again, I don't even know what she did that time, but it was for a very stupid reason, but I still understand why. Another 5 years of small slights and insults had built up and so she snapped at one of my friends. Afterwards, I found out that he was seriously afraid of me over that, from another friend. So I took her, and drew a picture of her chained down, and explained very sternly that she was not to come out again, ever. She hasn't. I think she may have tried once when I loosened the chains in an, er, experiment recently, but I figured that wasn't very good and reset them.
...Okay saying all that maybe it really does sound like DID but that's only one alter and one who is essentially gone so I'm not sure it would still count, would it? That was only one reason though, there are others, but less obvious.
I only have one friend I really talk to right now, and we get into arguments sometimes, that's normal right? One seemed to be pretty big and we stopped talking for a while but that's been over with for a while. I don't know what we were mad at each other over, and I know I don't want to know, but I figured that was just typical memory blocking. That happens, right? Well, that's what I figured until I realized just now that I don't remember what we were arguing about a few days ago. I remember it happened, and I remember how we dealt with it, but I don't remember what it was, or I just don't want to... Is that still normal? Is it even normal in the first place?
The last is a bit of an odd reason, I think, but I'll list it anyway... I roleplay sometimes, and recently I ended up with a character who has DID, but that wasn't really my intention, it just kinda happened. We just went with it for a while, and then eventually I wanted to make sure I was portraying it accurately so I started researching. I was really surprised when I found out I was actually doing it pretty well (according to the internet anyway). For one, I'd never even heard of co-consciousness before, and some other things I'd just made up but they all turned out to be perfectly viable (I can't think of other specific examples at the moment). While relieved, it made me rather suspicious that I was able to just "guess" that well.
===
Now for some reasons opposed... Well, the main one is, I actually do remember my childhood, quite a bit of it apparently. When I was younger I used to say that I had a good long-term memory and a bad short-term one. That still kinda holds true, apparently, though I had my doubts for a while. Middle school is a bit fuzzy, but that was a dark time in my life and I'm fine with pretending that never happened. (I do remember it happening though.)
Other reasons opposed... Well, I guess I just don't ever feel "switchy", not like those times I mentioned above. Sure I get mood swings sometimes, but that happens to lots of people. And other than the stuff I mentioned above, I don't really get gaps in my memory, or at least I don't think I do. Maybe just none that I can remember, ha. Anyway, it seems to me that, if anything, I'd have to be co-conscious without realizing it, and that sounds a bit strange to me. Is that even possible? I guess I should say that I do have conversations with myself a lot, but that has never struck me as being something odd...
More reasoning opposed, adding down here because that's when I thought of it. The angry me up there could be just that, me losing my temper. Maybe the circumstances are a bit strange, but I wouldn't know. Well one extra thing, I used to not be able to hold a grudge. I'd tell this to people like it was a virtue, but in retrospect that might not have been a good idea. Well, I got really offended for the first time a few years back, and since then, grudge-holding has not been a problem for me.

===
That ended up longer than expected, my apologies. To anyone who read it all, thanks. I'd really appreciate your feedback.