Is This Why

This happened to me.

I was hauling a bunch of stuff, one kilo per package. I was within
weight-and-balance. But one by one they slid to the very back. They were
left on the conveyor belt rollers by mistake.

More kilos slid, the center of gravity moves aft, So I dialed in more
nose-down trim. Soon..no decalage. I got careful.

She wouldn't maintain airspeed. I thought I was going to rip the plane
apart. But I did not. I thought she would stall. Then the nose pitched
up. I pushed on the steering, more stall!!

We opened the side do0r (I know FAA regs ouch) and threw the "stuff"
out. All was ok.

Why did the nose pith *up*? Why did adding flippers not work right?