I'll see about moving his appointment up, but it's hard since the husband and I are usually working the same hours as the vets office and they're closed on Sunday. I'm only off on Sundays and Mondays, so it's a bit of a challenge to get him in.
He's 2 years old and had his last bordatella shot in March. Nothing has come up with his heart in any previous visits and he's certainly not exercise intolerant in any way. When he's at the park or my parents house you wouldn't know he was tired at all until I get him into the car where he finally lays down and rests, and if the park is full of other dogs he'll resist attempts to leave until I catch him, even if we'd been there for over an hour.