You should have 2 sides to you tank, a cool side on one end and a warm side on the other. You should have ideally 2 identical hides, one on the warm and one on the cool. Both the heating pad and light should be on the warm side with a thermometer with a probe in your warm hide to keep track of how warm it is in there. That way you won't have to worry about how warm it gets in there.
Also you should have some sort of rheostat or thermostat hooked up to the heating pad so the temp doesn't get too warm if the room warms up.