A couple things... you said your thermostat probe is taped directly to your UTH. What are you setting the thermostat to? It should probably be set a few degrees higher in order to obtain a proper warm side temp as you lose a few degrees going through the plastic and substrate.

Your newspaper substrate should only be a couple pages thick.

The thermometer probe should be placed over the substrate in the warm side hide in order to give you an accurate measurement of the warm side. The hide will often trap heat so if you try to get the warm side to the low 90s, the inside of the hide will be much warmer.

Also, what kind of UTH did you get? Is it designed for reptiles?