Stressed gecko?

Question
I have a 10 month old female Leo Gecko. She has recently started to dig in her cage. I have read that the cage is to small, I have a 10 gallon tank. I am getting a 20 soon. Is it possible she is laying an egg? If she is, how do I tell? I was recently watching a male (we think) Leo for my friends. They went on vacation... I let the 2 be together. They did not seem to have intereset in each other so one night I let them be together. Is is possible they mated during the night? Another thing, she only digs when her light goes off.(Is that because she is nocturnal?)    
Please help!

Answer
Hello Sela, thanks for all of the information. It could be because of the size of the tank however most Leos are fine in a 10 gallon. It is possible she is "gravid" (reptile pregnant) and is digging for a place. However she doesn't seem much of the age for doing so. It might be too hot for her. In the wild they dig under sand and rocks to get down under the heat. How warm is it in her tank? Does she have a hide spot with moist paper towels? Make sure its not too hot. It is probably because she is nocturnal and doesn't have the energy during the day. That and they see much better at night.