Wis- i don't actually black-out with mine but i can relate to the sparkles, dizziness etc... i am a bit disappointed that you did NOT go to the ER from school. you still haven't been properly diagnosed. i know that a doctor does little neuro tests when one is having a migraine and asks a lot of questions as well. she/he will shine flashlight into your eyes and have you follow it, check your balance, hand strengh, reflexes etc... if he deem necessary, will order a catscan or send you to a neurologist which is a dr who specializes in brain/nervous system.
i don't want to sound like a nag but... i am worried about you! you need to be checked out! it could be migraine or it could be something more serious! you should not mess around with your health.
also- about not "being popular". well, EVERYONE in high school has insecurities!! even the "popular" ones. please try not to be so hard on yourself! pink has a song called, "i'm a hazard to myself". i think everyone your age could relate to it. i remember some of the girls in the "prep clique" thought I was a snob! ( i saw it the other way around! ) you shouldn't worry what other people think because they are probably too worried about what others think of them to notice anything else. the teen years are about finding yourself- not trying to be like everyone else. hold that head high, check yourself in the mirror and say, "darn, I am a fox" and get on with your bad self!
you haven't told us what your parents/guardians are saying about this! by all means, get some medical treatment when these episodes occur! i think i can safely speak for everyone that we are worried about you! TAKE CARE OF YOU and SMILE! my motto is "fake it til you make it!". chin up and you are still on the prayer list!