Go in relaxed with the conception thing. I don't think you need to have understanding of it. Whatever comes up, comes up. If your alters are talking about it, then there is something inside that needs to come to the surface. And EMDR can help it come up and get handled.
The way EMDR protocol works it probably won't matter if your protector is balking. You will keep being called back to the target. Also my alters come out during sets all the time thinking they can't be helped, but they/we/I end up helped anyway. My protector has come out during sets and told T that EMDR is BS that will never work. That was quite a long time ago, when we first started. He trusts T now.
I sympathize with feeling like you are only partially there. That happens to me a lot in therapy. And I have described it the same way, like being under water!! I
think it happens when one of my parts has moved in and is doing therapy with me. It's not exactly what I would call co-conscious - though I experience that too. It's more like an in between spot...between a part taking total control and having total amnesia as a result, and co-conscious - being able to remember it well. I come back with a vague impressions. T will say "Fantastic! You had some wonderful insights!" And I'm like....Oh yeah? Could you tell me what they were, because I don't remember!" Right now, I couldn't tell you one thing about my session last week. But I remember being there the whole time. Strange feeling.
I'm really excited to hear about what happens with this line of action you and your T are on. If you are comfortable with telling I would love to hear how this all turns out for you. Even if it were to involve pre-birth trauma memories, it wouldn't surprise me, because I believe in that. Crystal