Mid life crisis maybe?

My 3yr old guinea pig just isn't acting like himself anymore. When I go to let him out of his cage he'll simply stay in one spot or crawl under the couch to sleep. He used to popcorn a lot and squeak loudly. Another thing too, he coughs a lot and hurts easily like I would be gentle as possible when holding him, but he'll let out a squeak as if I'm hurting him even when I'm trying to be gentle with him. I don't know what's wrong with my poor baby is he getting old? Should I take him to the vet?