Pcos but blood test said I didn't have it

Ok so my dr did an ultrasound and he said I had pcos but I did the blood test 3-4 months b4 that and the tests came back all negitive I even had an ultrasound done at the er and they said I was negitive for pcos but I did have some cycts but none significant. I'm not sure if I've been misdiagnosed or if pcos happend within months of this all happening . He put me on birth control to regulate my cycle but I'm starting week 3 and I started to bleed . Did anyone else have a negitive blood test but then was diagnosed with pcos ?