Take of rotors

I have a 1998 GMC 2500. Everything runs fine but one day i noticed a grinding coming from the front right brake. I took the tire and caliper off to find that the inside brake pad had worn down to bare metal (I don't know how this could have happened since i checked the pads two months ago and they were fine). i bought a new rotor and pads, but i can't figure out for the life of my how to get the rotor off. i tried a puller but it just pushes the axle back. i'm pretty stuck. if anyone could let me know i'd really appreciate it. thanks

It is possible if it got hot enough that it "welded" itself to the spindle or axle)depending wether it is a 4x4 or 2wd