I Messed Up, And Tried Cocaine The Other Day (3

I messed up, and tried cocaine the other day (3 small bumps) other than that no drug use for the past 2 years (i used to smoke pot). I may have a hair drug test coming up at the earliest 2 months, latest 4 months. If i shave my body hair (im bald up top) in a week or 2, and let it grow out for the 2-4 months, will it test positive for cocaine? Or will this hair be "clean"? Please help.