Should I Take My Dog To The Vet If He Is Panting All The Time?

Maybe he is hot - with a fever, or pain. Is his stomach swollen? If so I would suspect bloat and he needs to see the vet.
If his stomach is OK, do you have a fan cooler that you could blow on him? Or a cold pad?
If none of these ideas fit - can you give us more information, like his age, breed, behaviour.

He might have a diseased or malfunctioning lung;get him to a vet immediately.

Dogs pant to get rid of heat, to cool down. But panting all the time is not normal. You do not say if your dog is one of the flat faced pedigree breeds, who suffer from breathing problems. You really should take him to be examined by a vet.

Dogs pant when the are sweating or warm. Dogs do not perspire like humans to cool themselves but maintain their internal temperate by panting. It is normal for a dog unless there are some other undisclosed issues.