We usually keep the house temps at 68-69, it's been that way for quite some time and it seems that Ernie's fine with it. However, it is pretty cold outside.
I'd say he's cold. I have a $7 heating pad over my bird's cage, and it seems to help. Magnus seems to be lethargic and not as active when he's cold and he will tremble a bit. I say he's more comfortable about 4 degrees warmer than I like, usually.
Cover 3 sides of his cage with a blanket (make sure he can't chew on fibres though - I use a cotton bed sheet st the first layer and then a fleece blanket over that). And then cover his whole cage at night time (ensuring to leave room for air flow)
Also, make sure he is not right next to a window where draughts might be coming in.
However i would recommend having him checked over by an avian vet especially if your house is at a constant temperature.
Every night we cover him completely up with a blanket. And yes, he is next to a window but we got brand new windows recently and I don't think there are drafts. Problem is, we don't have an avian vet anywhere near us......I'll try covering his cage on three sides, but sometimes he gets upset.
If there are no Avian Vets near you, then you need to find a good Exotic Vet with experience in treating small birds in case there comes a time when Ernie becomes ill or injured.
Waiting until there is an emergency prior to doing the proper research is never a good idea.
Establish a good relationship with a vet for Ernie and ensure that individual also has the means to consult with an Avian Vet if necessary.