I had two big clues... I went to work one 'Tuesday' and clocked in as normal and got to work... it was a small, family owned retail store that I loved. That day was weird though The person who usually worked with me on Tuesdays wasn't there another woman I worked with was and not one person came over to say good morning to me. After about 15min one of the owners came up to me with the strangest look on her face and said we needed to talk, could we go outside. I said sure, put down my stuf and trotted out the back door. She stood REALLY far away from me with her eye on the door as she explained: We told you yesterday that you were fired and not welcome back in the store. After the violent, destructive fit you threw for no reason Tuesday I don't see how you could just show up today like nothing happened!" I explained that today was Tuesday and I had no idea what she was talking about and it was out of character for her to joke so could she please tell me what was going on... She said she didn't want it to end this way but I needed to leave the property now or she would call the police.
That was my first clue! Then I called some friend because I was crushed over not only losing the job but upsetting people I cared so much about and not knowing how. Well then each and every one of my friends had at least one story of when I did something with them and then when they went to talk to me about it I had no clue what they were talking about. One was a masters level psych student who finally brought up DID and said she had been wondering for a while but now she was sure.

I am a bit slow to catch on