When does the spirit enter the body?

[irpsit]

I can physically remember my birth so I was already on it (the body).

Pregnancy could be a state in and out, I think.
Conception seems to my memory to be a process that the spirit watches from mostly outside but touches with.

I cannot be fully confident of my statement. And it may be different for different people.

I know this was covered but can't seem to find it.