To answer your last question - strings, pickups, setup (frets, nut, pup height), physical materials of the guitar, lack of gain or compression in amplification, playing style etc. Not that I'm generalising there as that seems to cover "guitar and amp" :-D
I think we can rule out style as you say "it's the only guitar i've ever had it with" so I think we know you can pull them. Ergo I think we can also rule out amplification and effects as you can pull them on other guitars with your setup.
This leaves strings, pickups, setup, materials.
Please elaborate a little on:
- make and model of guitar
- build type (set, thru, bolt-on)
- pickups
- amp and effects
- strings
...and we'll try to pinpoint it a little further...
Do fretted notes sustain well? Do you have a high or a low setup? What bridge are you using (fixed, trem?).