My Dog, Has been vomiting on and off for the past couple of weeks, Yellow hy bile?

My old dog used to do that, (he was old tho) but you dont say how old your dog is, mine had something wrong with his liver, maybe thats why, but you wont know until you take him to the vet so i advise you to do so, a vet will only know for definite, with x-rays and stuff.