Having bizarre, irrational thoughts while entering or leaving the sleep phase is commonplace and related to hypnogogia/hypnopompia. It happens to me from time to time and I suspect it happens to most people. Perhaps you just notice it more or are more inclined to remember.
The thing with hugeness juxtaposed with tininess is something I've experienced as well, particularly during my childhood. For me it happens along with a sensation of eggshell-like smoothness and its conjugate, a crinkliness like crumpled paper. There is also a sensation of pure whiteness and perfect inky blackness. Anne Shulgin (R.I.P.) described a phenomenon similar to this in part one of TIHKaL. It seems to have various stages and levels.
Have you ever read TIHKaL? There's a whgole lot of useful information in the first part (as well as the chemical recipes in part two). From what Anne Shulgin has said, it may be worth relaxing fully into the experience and seeing where it leads you, minus any of that cognitive '
noophonic paraeidolia'.
“There is a way of manipulating matter and energy so as to produce what modern scientists call 'a field of force'. The field acts on the observer and puts him in a privileged position vis-à-vis the universe. From this position he has access to the realities which are ordinarily hidden from us by time and space, matter and energy. This is what we call the Great Work."
― Jacques Bergier, quoting Fulcanelli