You may want to search for a Gyno/Oncologist. I found that mine was more preventative than my (ex-)gyno, while still working to preserve my fertility.
My cyst is almost 30 cm now, but there removing it. My I said when it was at 4 cm that they would remove it if it got bigger.
I would go get another ob. That one sucked
Go to another obgyn ASAP! it could be benign, but what if its not, you're losing time! If you can't afford another gyno, go back to ER , explain them the situation and they will help you! Please don't delay, especially if you have symptoms.