First, how could you be out of school for a year, but only be alum for a semester? You cannot be active if you are out of school.
If you went back to school, then did you rejoin your chapter? If you never rejoined the chapter, then it's my understanding that you are still considered alum.
You should check w/ HQ on this, to see if you have left on good standing.
kappadelta@kappadelta.org or call the toll free number 800-536-1897.
If you stayed in school, pledged Fall 2002, then Spring 2006 would be the end of your 4th year.