blue tongued skink not pooping

Question
My 10 year old got a 3 year old skink from an acquaintance.  Their 17 year old son was no longer interested in caring for him.  We've had the skink for 2 weeks now.  He's in the same tank and has the same wter bowl. Although he is pretty fat from what I learned from the original owner and since from others, he hasn't really eaten since he's come with us nor has he pooped.  I have seen him take some water.  I've tried the food they fed him as well as new things I've read about on line.  I'm less concerned about the lack of eating than the lack of pooping.

Answer
Shoshi,                                                      This may just be because he hasn't eaten, but just in case force some mineral into him. He may have a piece of his substrate caught in him if he accidetally has eaten a piece... or if he is on sand may have ingested too much while eating. He needs to eat soon.... I hope this works. Tina