Hi, Killmanjaro!
It is the same with me: when I am there, "the places" seem to be so familiar to me, yet I cannot recall them from "this world" very clearly...
I don´t think you have been "preventing" yourself "from breaking through fully"... But I don´t think you took dose large enough... If I got you right, you vaporized 20mgs of DMT. I would say that for most people, 20mgs - even if vaporized properly in 1 hit through a GVG

- wouldn´t be a breakthrough dose.
I suggest you to increase your dose
slowly: 25mgs, 30mgs...
BTW: how do you smoke it?