If you actually have steam in your bathroom, your water heater is set way too high. And aren't the burns on your skin painful?
The last thing you want in your attic is moist bathroom air. DO NOT VENT THE FAN INTO THE ATTIC. Insulation will become saturated, mold will thrive, and you'll spend some serious bucks to correct the mess.
Far better to just check the fan for proper operation, and make sure the sheet metal duct between it and the outside is not obstructed by anything (including a malfunctioning weather flap on the outside). If it's undersized for the room volume, replace the fan with a larger one.