I have measured the resistance between the output sleeve and the strings (and the tuning heads and the termolo) of my guitar and got a reading of 0 ohm. So I take that my guitar is properly grounded.

Then i started my practice, using a headphone plugged into a LX12 Laney AMP (should be 10W?), which has always been working well. I heard that when my finger was put on the string or other metal parts of my guitar, i would hear less noise (electrical noise/signals). It is not about muting strings coz before i did that i havent picked any strings at all.

so my question....... why is this reduction of noise? is my guitar having any problem?
Ive had this same experience before. I think its just the electrical current running through the metal objects on your guitar.
this effect is a lot less obvious or nearly gone if i turn a nearby fluorescent light off