low blood pressure

i was at the station sentral yesterday having lunch with my 2 friends when all of a sudden i felt like blood rush going up my face, my head, and heart started to pump so strong, i felt my face warm, and light headed... felt a bit sweaty and nausea. i stopped eating immediately and my 2 friends asked if i was okay. i felt like almost black-out. i did not finished my mushroom soup - garlic bread - ice latte. was it because of the combination of food? or was it because of the pain killer i took the day before? 

when i got at the office, i was still feeling light headed. normally when i feel like this my blood pressure could be low. so i smsed joey and told him that i am not picking him up from his school today because he normally stays back. i got home, had my early dinner - at 530pm :P as i didn't take proper lunch. and watched tv on the sofa.. which in the end, the tv watched me :p

let's check what could be the reason of low blood pressure.