Seeing floaters. Opthamologist said my eyes look fine. I've had dark spots in my vision before, and have seen a circular, colorful, jagged line also.

Migraines. This could be an example of an ocular migraine which can cause visual symptoms without an associated headache. If the symptoms are infrequent you can simply observe but if they become frequent you can see your doctor for treatment.
Floaters not harmful. But may be accompanied by retinal tears, detachment and occasionally vitreo-macular traction. A dilated retinal exam should rule out any urgent issues such as the retinal tear or detachment. The other effects may be due to adhesion between vitreous and retina. If those signs persist, have another exam to look for tears.