What is 75 degrees? The hot spot?
Sounds like your uth needs to heat up. I hope you have some kind of dimmer on it because the problem will be too hot if it is working properly. An UTH is all you will need for the hot spot, and maybe the light will bring up ambient temps, but be careful because the light can dry out the enclosure really badly.
What kind of substrate are you using by the way? Is it one of those 'add water' type? Coconut? Those can take a long time to dry out sometimes.
When do you plan on getting a snake?