Our 15lb Chihuahua/Maltese mix has a gurgling belly. You can hear the noise just being in the same room as him. He is super uncomfortable, sits down for a moment- you hear a gurgle and he shoots back up and circles then sits down again. It happens about once a month and lasts for about 12-24hrs. We have taken him into our vet a few times for it but by the time we take him in it has subsided. I believe they typically give him a one time dose of an antiemetic. Most of the time we have him leashed & am outside with him so we do not believe he is eating something. No table food, eats science diet. Has regular, formed, bowel movements. Unsure of what to do or how to make him feel better! We can not afford to keep taking him to the vet & not have answers of why this keeps happening.
Maybe you can talk to your vet about a long term sensitive stomach food to try? Or make sure it doesn’t correlate with any of the preventatives you give. (And if you’re aren’t giving them you should check to make sure it isn’t intestinal worms with a fecal sent to the lab for analysis). Also some dogs benefit from probiotics long term and gi protectants. I can’t tell you what’s going on with your pup but I do think there are lots of low cost options to try to figure out what it might be. Also you should remove all snacks and treats for a month or two to see if this helps. I worry about gi issues and pancreatitis. In some cases there is excessive gas so a diet change might help. Talk to your vet about all of these. Let me know what happens. Good luck.