Could you give a full run down of the set up?
- Substrate?
- How is the tank heated?
- What are the temps?
- What prey items are offered?
I think this guy should go see a herp vet, there is definately something going on with him. It could be impaction, or calcium deficiency - or both. Calcium deficiency can cause issues with defecation because calcium is needed for muscle contractions - including the GI muscles. There could also be an entirely different issue going on - if his appetite is poor, he cant move his back legs, and he isnt defecating then whatever is going on is serious and needs to be addressed asap.
I would start doing warm water soaks a few times a day to try and help pass the impaction, if it is an impaction.
Its very important that the Leo has the proper temps - and that those temps are coming from the floor. Set him up in a hospital tank with paper towels as a substrate, an undertank heater with a digital thermometer with a probe taped to the warm side - the temps need to be 88-92degrees.
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1.1 Bearded Dragons
2.2 Leopard Geckos
1.0 Uromastyx (Mali)
1.1 Corn snakes
0.1 Mexican Black Kingsnake
1.0 Bairds Ratsnake
1.0 Rosy Boa
1.1 Green Anoles
1.1 House Geckos
0.0.2 Flying Geckos
0.0.1 Red Eye Tree Frog