What Causes Delay In Period?

hi... just confused and worried... haven't got my period up to now, my LMP was jan 11, 2014, negative pregnancy test, ultrasound result "there is a 3.52 x 2.32 cm thin walled cystic anechoic structure in my left ovary" what's this all about... my right ovary was normal...
am i still have a chance for pregnancy, i'm 41years old, D&C last 2010...
thanks
ieen