wouldn't you be messuring the substrate?
first calm down
chances are if it doesn't feel "hot" its not too hot. go stick you hand directly on it, does it burn you? does it almost burn you? if it does then i'd pull the plug and just try to regulate the heat by pluging it in and out. but if it doesn't feel too hot like you said don't worry.
If you got the money invest in a thermostat and it will take care of you. if not buy a rheostat and you can control the output of the heater, but you got to constantly check it because a change in room tempature will change the cage tempature
but no the ball python going to the cold end of the cage is not a sign its too hot... you don't put that hide there for no reason, they can use it lol