I would suggest this needs further examination at your vet. Hopefully, they will do an X-ray of her bowel and lung
area to see if it is a blockage - though of course, not all obstructions show up on an x-ray.
Just because she always seems to be at the vet, that's not a good reason for ignoring these symptoms - it may well be something and nothing, but equally, if it is something like an obstruction or a trachea problem, it will need professional treatment quickly. Let us know how you get on.