I was in your same spot in October of this year. Very Important I had my ca 125 test done and it came back a little higher than the norm. I was going nuts. I even went as far as getting an opinion from an oncologist gyno and he told he that cyst are abnormal cells and it can cause the CAT 125 to be out of the norm. I think what they also look at is your tumor marker. My cat 125 was higher and my Tumor marker was normal. Again I just responded to you but my cyst were removed and my pathology reports were fine. I know what your feeling! no worries try to keep busy and stay positive.So many women go through this so your not alone.
The iud could well have been keeping the ovary quiet and once you came off it your ovary was active to play silly buggers. If they are heavily concerned they will look to surgery. Key hole surgery or a three port laparoscopy is usually common and then they can biopsy the cyst. This is in the UK. X
Also, when do they typically look into surgery for cyst removal, over a certain size?