What Causes Colors And Objects In The Vision With A Smaller Right Pupil?

Hi im having the most unusual things happening to my eyes, im 18 years old and male. Sometimes i see a rainbow circle in the middle of my vision and then i start seeing absolute random outlines of objects, nubers, letters, words, ect. The outlines of these images are rainbows and if i think of a certain item or thing it pops into my vision and stays there till the next one shows up. I seen an eye doctor today and he said my eyes were very healthy and that i had 20/20 vision I d like to add that prior to this i would have moments where my right eye would have a terrible time trying to focus which would completely throw off my vision and sometimes give me headaches, my right pupil is almost always noticeably smaller than my left, any idea of what this might mean?