As titles says, the last time he panted like this he was in pain with limber tail syndrome. He's also trying to sit on my lap, rather than just rubbing his head on my knee haha. I've checked him all over and he's not yelped or whimpered, but his tummy feels a bit hard. Equally, I don't press on his tummy that often, so I'm not sure if it's supposed to feel like that!
He's a black lab so the worry is always he's eaten something that's got stuck, but I haven't noticed anything chewed / missing and he's not done that in a few years (bar some long grass / straw that needed me to 'help it out' 
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Any ideas? Otherwise I'll keep an eye on him and hope it's just trapped wind...