I laid down and told myself that I will not move until I'm in a dream.
I think it's worth noting that I was WILDing on my back, even though I have never been able to fall asleep on my back.
It didn't seem hurt your attempt, but it seems like you were more focused on WILDing than falling asleep, and if not then disregard this. It should be a point to make sure you can fall asleep. Don't think or worry about not moving, because you don't normally do that when falling asleep. You also don't necessarily have to fall asleep on your back, and it would be better to sleep in your regular position, as long as you're comfortable enough to stay conscious throughout it.

It seems like you were in Non-Rem sleep and hypnagogic imagery started settling in. It might help to actually roll over, and despite it reversing your progress a bit, it'll probably be worth it. Being comfortable is priority when sleeping, so if there's pain or anything like that, get rid of it and continue.

EDIT: Or you could just go with OpheliaBlue's suggestion. That works too.