I have some very very young alters who act out and try to talk with T about their trauma although they have very limited vocabularies. They sometimes try to draw pictures, althou the pictures are hard to make out. Maybe drawing would help?
I believe you can remember things from that young. I have clear memories back to two weeks of age, which my mom was able to help me figure out how old i was based on how much my nursery was decorated at the time and what i was able to tell her about.
I hope you can talk about this stuff with your t.