I had a ultrasound done last week, & a 5.8 solid mass cyst was discovered on my right ovary, which the doc said doesn't look cancerous.

Only one way to know: Unfortunately with these masses the only way to know for sure what it is, is to undergo surgery to remove and examine the types of cells involved under microscope. If it's a round mass w/out any other lumps/bumps then maybe it's benign but no way to know for sure. You can consider observing it to see if it gets bigger in a few months or you can plan surgery. These masses can twist and cause pain.