My dog's belly is swollen and rock hard and he keeps trying to vomit but nothing comes out

Go to a vet or an emergency clinic now, tonight, and have someone phone the clinic from the car while another person drives, so the team is ready the moment you arrive.

That picture — a hard, swollen belly, retching that brings nothing up, heavy drooling, restlessness, pale gums — is what a twisted, gas-filled stomach looks like, and it is measured in hours. The stomach fills, rotates, cuts off its own blood supply, and the dog slides into shock while the belly is still getting bigger. It is treated with decompression, intravenous fluids and surgery, and survival falls with every hour of delay.

So: no food, no water, nothing at all by mouth. Do not walk him around the garden to help him pass the gas. Do not wait to see whether it settles, because it does not settle. Carry him or support him to the car if you can — a dog going into shock who is made to walk can collapse. When you call, use the words possible bloat, retching but no vomit. That phrase gets a dog seen ahead of the queue and lets them prepare.

Deep-chested dogs are the classic ones, but any dog can do this, and it often follows a big meal or a big drink and activity. If you are wrong, you have spent one consultation fee. If you are right and you waited for morning, you have spent him. The exam and usually an x-ray settle this in minutes — not a guess from a distance.