CHICAGO (WLS) -- A Chicago mother is asking for help in finding her 18-year-old son who's been missing for more than a week.O'Shai Royal, who has bipolar disorder, left his family's home Feb. 2 and was last seen near East 44th Street and State Street.Royal's mother keeps thinking he'll return to the house."I just keep looking at the snow at the back porch and just looking out my back window and he's going to knock on the window or come through the door and i heard him the other day but i didn't see no footprints in the snow," said his mother Sherry Bryant.Royal is 6' 1" and approximately 150 pounds.Anyone with information should call 911 or Area Central Detectives at 312-747-8380.