leopard gecko not eating his crickets

Question
My leopard gecko hasn't been eating his crickets only mealworms and is laying under where the uv lamp is placed all day for two days straight. When I bought him he looked only a couple of Weeks old and I've only had him for about two Weeks , this is the first time he does this , is something wrong with him ?

Answer
2 days isn't very much time, but a little troubleshooting is in order.  What are the exact temperatures in his cage, and how is it heated?  What controls the heat source, and what type of thermometer do you have?  What are you using for bedding, hides, and furnishings?  How often do you feed the gecko, and what size insects are you using?  Are you using any supplements?  Is the gecko being handled?  How is the gecko's tail weight?  (A leopard gecko should have a nice, fat tail).  Where did you get him?