strange behaviour in leopard gecko possibly ill

Question
i have a leopard gecko around 5 years of age who i believe has been acting unnaturally recently. it started with him biting his tail which i believed to be normal untill that night he seemed daized only kept one eye open and left its food aswell as being very weak (noticed by him struggling to walk). although i believe this to be either me being over concerned as hes never bitten his tail like this or something relly is going on. this may be due to other issues as well those which i believe to be a conern are that he has been without a uv light for around 2 weeks and i fed him a wild grass hopper found in the garden (he usually eats medium sized crickets). i would apretiatei it if you could write back with your opinion on whats happening. all this happened within 24hrs and around 12hrs after biting his tail

Answer
Hello Reece,

Well, I hope that the wild grasshopper did not have any pesticides or chemicals on or in it.  Feeding wild insects is not recommended due to chemicals, etc that they can ingest.
Does he have any retained shed that you can tell of?  
The UVB light should not make that much of a difference though, not like that.  Using a low output one is a good idea though, as I always did use UVB with leopard geckos, too.  Do you use calcium supplementation as well?
What are his temperatures currently in the tank?

Tracie