What Causes Delay In Menstruation Other Than Pregnancy?

hello. i am currently 16 days late for my period. i am trying to concieve and have been doing so for 6 months now. i have been late before but onky by abt 7 days. thats about for me i never miss a period completly. my last period was oct 24 which was week late. i do not have any pregnancy symptoms. only slight cramping and alot more white discharge. i have abnormal and i am due for a coloscopy in a few weeks. havent taken a pregnancy test as yet but plan to do so tomor. do u have any ideas what may be the problem.