STYLETHREAD -- LET'S TALK SHOP!

Ovarian cysts are really, really common.  They occur when you ovulate each month - your ovary 'ripens' an egg, and when it releases, a pocket is left where the egg used to be (called a corpus luteum cyst).  The cyst produces progesterone (to sustain any pregnancy that may occur), and sometimes instead of going away when you get your period, they hang on and get large and fill with fluid.  No real reason why.  They can be painful, but in most cases they are harmless and don't require intervention.  They usually fade in 1-3 months, and your doc might want to do a repeat ultrasound during that time to check on the cyst and make sure it shrinks instead of grows.  Birth control pills are sometimes offered as a preventative treatment, because they prevent you from ovulating and therefore can prevent recurrent cysts from forming.

No worries .  Hope you feel better soon though!