>>The thermometer is in the middle of the cage on the left wall and it reads 70-75 throughout the day, another reason for the 100 watt is because my house is relatively cold.
Where is the light relative to the left wall? Basically you want to be sure you're getting the temp in the hottest part of the enclosure, and you want it never to exceed 80-85 degrees F, with about 75-80 being preferable. During the day, mine hides a lot (usually I can see a foot or a tail or something through the leaves, but they typically do hide during the day). At night, she sometimes hides and sometimes is all over the place. Another thing to check would be your humidity levels - I have noticed that mine hides more if her humidity drops too low. As long as you're sure that the environment is set up properly, you shouldn't be too alarmed if s/he hides a lot, as long as you can see that food is being consumed and poop is being produced; every gecko has a different personality, with some being much more outgoing and/or active than others.
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0.1 Albino Leopard Gecko - Tigger
0.1 Crested Gecko - Pooh-Bear