I'm not a doctor, so I'm just guessing here. It could be a bleeding stomach ulcer due to stress or excessive drinking, it could be a ruptured blood vessel in his stomach due to excessive vomiting, or it could be an esophageal varice. Let's pray it's not the latter, as this is the most serious condition of all.
I lost my father to an esophageal varice (a ruptured blood vessel in his throat) last August--due to esophageal cancer, not alcoholism. He began to spit out small amounts of blood around 11:00 pm one evening. By 3 pm the next day he was gone. The doctors were unable to stop the bleeding and he bled to death before my eyes. It was a horrible sight to witness.
In younger, healthier patients esophageal varices are life-threatening but, if they are caught early, they can cauterize the blood vessel to stop the bleeding and surgically implant an esophageal ring to prevent future bleeding episodes.
A stomach ulcer is a medical emergency, but they are generally not life-threatening when caught early. A ruptured blood vessel in the stomach due to excessive vomiting usually clots and stops on its own when the vomiting gets under control.
Sending prayers to you and your boyfriend. The hospital is the best place for him to be now. He's in good hands and I know the staff there is doing everything they can to turn the situation around. Is his family keeping you up to date on his condition? The new privacy laws were a great hinderance to me when my boyfriend, Richard, was hospitalized due to alcoholism last October. They would only discuss his medical condition with next-of-kin.
Please give us updates as you receive them.