hi having a cyst that has not gone away with medication is not a functional cyst. determine if it is dermoid can be at laproscopy which will be curative as well. the definitive diagnosis is based on pathological examination of biopsy specimen. anyways you have had a baby. should it be difficult to remove the cyst alone due to surgical difficulties  encountered then only ovary  might be sacrificed. with remaining ovary in that eventuality u can become pregnant.more than all this in  your case on view of the size undergo operation immediately so that torsion of the ovary and other complicatioes dont happen.