Leopard Gecko not moving hind legs

Question
QUESTION: My 9yr old son has a leopard gecko that is aprox. 7months old.  Two days ago, we noticed he was shedding but yet not using his hind legs. He appears to be dragging his back legs.  If I touch his hind legs, I am able to bend them, but he does not do it on his own nor does he try to move them from my touch.  He is really not eating like he normally does, but I assume that could be because he is still shedding.  I did put him in warm water to help loosen the dead skin.  He was biting today, and has been hiding more.  He eats mealworms daily and receives a dozen of calcium sprinkled crickets weekly.  I called the pet store were we purchased him and all I get is "Oh that sounds bad".  He is devastated and I am at a loss.  Please can you help me?

ANSWER: Hello Angie,

Hm, well, what type of substrate are you using, is it sand or other loose substrate?  What have you been feeding him?
Are you keeping him warm enough in the tank, & what type of thermometer are you using to measure the temperatures with?  
Could he have gotten injured possibly on something in his tank?

Tracie

---------- FOLLOW-UP ----------

QUESTION: Tracie,
The bottom of the tank is...don't know what to call it but it is the eco-friendly....looks like a piece of felt but it isn't.  He has always had that.  As mentioned above, he eats mealworms daily and calcium sprinkled crickets weekly.  His temp is 78-82, and measured by a digital thermometer.  The only things he has in his cage are: Plant for hiding, log, and his food/water bowls.  I have called the pet store AGAIN to see if they think it is a calcium deficiency, but appears that all they know how to do is sell you the animals. Nothing has changed within his cage since we got him 7 months ago.

Answer
Hello Angie,

Ok, the substrate is solid then?  That is good then he probably is not impacted.
However, he does need need a hot spot on one end of the tank of around 88-90 to help him digest.  
It is possible that he has a calcium deficiency yes.  Perhaps you could get some liquid calcium, or try getting a UVB light such as the Reptisun 5 or 10 tube bulb to help him out.
If he has not been getting enough calcium, he is probably low in calcium.  
Do you keep a small dish of calcium in his tank for him to lick when he needs more?
I know, I am sorry that pet stores are not more helpful most of the time.

Tracie