Multiple Ovarian Cysts and CA 125

Hi,  I went to the dr 3 months ago for a vaginal ultrasound and they said I had a 4 cm cyst on my right ovary.  They sent me for a CA125, which came back normal at 33.  They followed up a month later with another ultrasound and the cyst was down to 3.5 cm.  They just did the third ultrasound and said there are now two 2 cm cysts on my right ovary, and a 1 cm cyst on my left ovary, which all appear to be simple.  But the dr said he was still going to send me for another CA125 in a couple of weeks to follow up, so he could rest easy at night.  Does this mean there is a chance this could be ovarian cancer?  I am on Tamoxifen for follow up treatment to breast cancer, and have read that this can cause multiple ovarian cysts.  Is this true?