Our 9 year old bicheon never poops in house, but has recently done it lots of times,we have a new carpet but he keeps away from it.

Has your dog been to the vet recently? Any change in behavior should always be checked by the vet for any health problems.

Older pets can lose control of their bowels, its called Fecal incontinence. They have no idea they are pooping until they are in the act of pooping. Dogs that go from house trained to not house trained, that's the first thing on the list to investigate.