REVERE – Somerville police are investigating how a 21-year-old Revere man was stabbed multiple times in that city early Monday morning.The victim transported himself to Somerville Hospital shortly after 4:30 a.m., where doctors called police.The victim, who police would not identify, said he was walking with a friend on Glen Street when he got into a confrontation with a group of men, who assaulted them.As of Thursday, no arrests were made.