It does sound a bit like megaesophagus, Sophie. Echo had developed it shortly before she had to be PTS and had all the symptoms as described here. However, she also couldn't drink and drooled a lot as nothing could go down...not sure if that is normal or not, but that's the only thing telling me that this Bulldog doesn't have it as there is no mention of the latter symptoms.

She could always try and change the food again, but I also don't think it is food related. I honestly don't know what it could be, but I hope everything gets figured out soon!