Need handmade On Air Bed Sensor

Hi. I have airbed (air mattress).
Would like to have sensor which can detect if i placed on it.
Tried to do something like by layers:
air bed
aluminium foil layer connected to analog pin/vcc/gnd (tried differect combination)
textile
aluminium foil layer connected to - analog pin/vcc/gnd (tried differect combination)
wooden floor

When i just placed on bed values goes up but after some time goes down even less then arranger value.
And one more issue: analog PIN gives sinusoid values.
Maybe need some capacitor and coaxial cable... (i'm noob about about electronic btw).
Any suggestion how to detect when i placed on air bed?
Thanks

you need an air-pressure sensor I think.

i have no good way to put sensor inside.... need some kind of external one...

put a load cell underneath?

i think hard to do with load cell, cuz weight much depends where ur body placed on bed(queen size)...