My lab has been vomiting since April 29th. Lost weight from 83lbs to 79lbs. He has been to the Vet for X-ray & blood work and was negative. They've changed his Senior Nurtrience food to Gastro Can /Gastro dry food.

At first he was vomiting his food during the day and it was food vomit pickup. The Vet changed his food to the Gastro Can /Gastro Dry food and was now vomiting only during the night and is a yellowish vomit. It was only once in awhile too but now we've been vomiting 5 days in a row waking up to a vomit pickup, yellowish color.

If he doesn't vomit during the day why is he during the night?