How do I know if my dog is in pain?

My dog is more reluctant to play or doesn’t want to go out for a walk

My dog has difficulty going up stairs or climbing on to the sofa

My dog has developed more aggressive behaviour with other dogs or people

My dog rejects being stroked or having its coat brushed

My dog does not eat or drink like it used to

My dog is acting strangely

My dog is shivering, even though it isn’t cold

My dog is constantly licking or chewing part of its body

My dog has difficulty finding a comfortable position to sleep in