Complex cyst

I was just diagnosed with a complex cyst sized 4.1 x 2.8 on my left ovary.  This was found with a CT scan that was looking for problems with my gall bladder.  This cyst was not there 4 months ago in November.  I had 2 ultrasounds in October, 1 for my ovaries and 1 for my gall bladder.  The only cyst at that time was simple and tiny.  The next week my ob/gyn did laprascopy surgery to look at the fibroid on my right side and to get rid of endometriosis.  I am 35, have 3 kids, my tubes tied in 1991 after my last child was born.  Had an endometrial ablation done in 1999 to stop the heavy bleeding.  Could you please tell me what a complex cyst is.  Is there reason to do an ultrasound.  I go to the dr Tuesday morning.  The nurse told me it would have to be surgically removed.  Did  she mean the cyst or the ovary?  Its weird that it was found by accident.  All of my pain is on the right side and around my belly button.

[Gingham Girl]

Thank you so much for giving me some information.  Tuesday can not come quick enough for me to see my dr.  This is what my CT results read, if this would by any chance shed any more light on the matter.  

There is a 4.1 x 2.8 cm thick walled left adnexal cyst with a Hounsfield attentuation of 29, complex.  What does that 29 number mean?