ferret troubles!

[facade]

so, i got my ferret last spetember(late september)/early november.
things were going great with him! we brought him home,
and he already started going to the bathroom in the liter box,
no mess ups what so ever..
recently, at least a month ago..
he kept going to the bathroom in another corner.
i had originally thought it was the liter box, because it seemed like the liter box was leaking.. so i thought he was smelling his pee like in the other corner.
so, we got him another liter box... he still wouldnt go in it.
we finally gave him some medicine (i believe it was amoxicillin) in his water.
it seemed to have worked for a while, because he stopped going into the
corner and in the liter box..
but then he started going in the corner again, and the amoxicillin was still in his water.
this has been going on for at least a month now..
and we dont know whats wrong with him..
have any ideas? did you have a similar experience? /:

[ALLorNOTHINGforCHRIST]

I would have to say take him to the vet. It could be that the medicine needs to be in a different dose or that he needs another kind or a different diet.