Whats wrong with me black-outs?

ok sometimes when i get up in the morning and stretch on my tippy toes with my arms stretched all the way to the sky everything will go black for a few seconds an make me wanna fall right over on the bed....THIS dosent happen in school but even when im just in a recliner it happens tooo. ive ped out once in my life and...almost another because i was going to the bathromm straight across the hall from my room and half way from my bed everything went black an all i remember is sittin on the bathroom floor felling weird...need help im eating right too. sorry so long