Can you give more details of the situations when he pees on the couch?
Well, it happened in two occasions in two different days. The first time we had been playing, we had gone for a walk after, we came back home, then I went to the kitchen to have some water and when I came back to the living room I saw him getting down the couch and voila! He had wetted the couch so I took him out right away. The second time was yesterday but I just noticed that the couch was wet, but did not see the moment it exactly happened, so I can't give many details. But I find it extrange, as mentioned, since he has been doing really well on potty training, I wonder what makes him peeing there.