If your using some type of add-water substrate, you really should wait for it to dry out before adding your snake to the enclosure. The snake can get belly rot from too damp of a substrate. Also, if the substrate is cold along with the dampness, he can develope a RI.

As far as your temperature goes, maybe your thermometer isnt in the right place. Use a thermometer with a probe, and place the probe right above the glass where the UTH is. A lamp dimmer or thermostat will eb needed for the UTH.