Are you trying to figure out if you dissociated while writting the joutnal entry? 1. We can't really tell you that without reading more context. (Which you probably don't want to share that really detailed stuff here)

I think it is possible for people who SI to feel like they are dissociating. When you SI as you most likley know your body releases endorphenes. Kind of giving you a natural high and floaty feeling but without the memory loss or time loss that comes with dissociation.

When I used to SI i would feel like i was watching myself SI someone else. This is called derealisation. Sometimes I even felt like I was even SIing an inanimate object.

I don't know if any of this helps.... Also maybe look back in your journal and see if there is a pattern of topics where you are more likely to write in first person and ones where you are mostblikely to write in third.