I will not question your experience but I will ask you (or anyone else) to provide a solid Scriptural basis for "being slain in the Spirit". First of all that term does not appear in NT Scriptures, and secondly whenever Jesus or the apostles touched someone, they were lifted up, not thrown down backwards. Those who were overawed in the presence of Christ fell forward on their faces.
The ones who fell backwards had come against Christ to take Him captive but could not do so until He allowed it. As Got Questions says, this experience is "a bizarre counterfeit".
To be honest I can't explain it.
If memory serves me in those days people were positioned to catch people.
So in a sense of was like it's gonna happen.
When I went forward it was actually something to me that I did not seek and was resistant to it.
I just wanted prayer.
So there was no one behind me to catch me.
The guy put his hand on my head and I just fell down.
What I do remember though is that I was fully aware of my thoughts.
I was also fully aware of a peace that came upon me.
I was fully aware enough to pray "God help me, I need you so much"
I went away with peace and reassurance that God actually loved me.