I don't vomit often, maybe once a year (from drinking too much or whatever) but whenever i do there is some blood in it. serious problem?

To be avoided!: Usually a small amount of blood in vomitus after drinking is due to the inflammation of the esophagus and stomach caused by the alcohol, followed by the trauma from the act of vomiting/retching. An isolated occurrence of a small amount of blood could be expected. But obviously this is something to be avoided! If more than isolated/one episode, see your doctor.