Can you tell from an ultrasound if an ovarian cyst is benign? i have cysts and my doctor doesn't want to do surgery, can she be sure it's not cancer?

Depending: on the presence or absence of certain sonographic features, a cyst might be able to be characterized as benign with a high degree of confidence, or on the other hand, might be characterized as suspicious for malignancy. Or it might be indeterminate. Management also depends on your age and clinical history. A cyst in a young woman is almost always benign.