How/where are you trying to feed it? You could try feeding it in a seperate, small container so the snake has nothing to concentrate on but the pinky over night. Like a plastic butter/margerine container, or something of that size, with air holes. Put in inside the regular tank in case it escapes. This is supposed to work about 50% of the time. It doesn't work on my corn snake though, so you never know.

If it's been three weeks, I would say go ahead and try the live pinky, as led said. It couldn't hurt your snake.

Welcome.