My dog (old english sheepdog) is about 7-8 years old male. He has recently been doing this thing where it sounds like he is trying to hack a loogie. He was put on a sulfa drug 5 days on 5 days off, twice a day. He seemed to be getting better, so we stopped with that cycle about a week and a half ago. Now today, he threw up his breakfast, and now has thrown up bile a few times. Do you think you could explain what this is? How to treat it?