Two days ago, my dog was downstairs in his bed, I ran upstairs to take an urgent piss when I heard him yelp. I went downstairs to find him lying in the middle of the living room with a sorry look on his face and shaking. I couldn't work out what he'd done, so put it down to maybe stepping on one of my sons toys. Since then, whenever he gets up from lying down and goes to stretch where he pushed his front legs out in front with his butt in the air, he yelps before he gets half way down. He also squeaks as he runs up the stairs now, but not down them. Yesterday he went out to greet the postman and put his two front paws on the 3ft wall as he does, he yelped straight away and came running back into the house. He still wants to go out for walks, but I've been keeping him on the lead to stop him over exerting himself, he doesn't limp or favour any foot. He's not off his food, so I'm convicned he's either pulled/strained a muscle, or worse, he's injured his back.
When he's lying down relaxed, I've stretched each leg out gently to it's full extent and he's not made any noise, he pulls back with his legs, but I'm sure he's always done that.
He's a dalmation rotweiller cross, 6 years old.
Here he is with a "please help me get better face"