I've no idea how I did this

I was doing a few minor jobs on the MV6 this evening, as it's well overdue an oil change etc. After I'd done all the work, I somehow lost my footing. It was too late to do anything, and I went over backwards, on my tarmac drive.
Unfortunately, the very lower part of my back (Eg, just above the @rse) landed with my full body weight onto my 3 tonne trolley jack. It landed on the bit where the handle goes in

Here's the scary thing - I blacked out. I didn't hit my head at all, ini fact, I blacked out before I hit the deck.
Ten mins later I was laughing with a cuppa, but now I am in absolute agony, and the lightest finger touch in that area (oo oer) causes me immense pain.
I think I've broken the little bone in the rectal area - coxix or something?

At the moment, I'm like a bulldog who's swallowed a wasp...
