What Causes Sudden Lightheadedness, Increased Heartrate And Vomiting Sensation?

HI , I am concerned , I was at an event earlier today( a funeral) . Saying good buys , I suddenly felt a little light headed. ( i have had a siezure in the past , So i am vary sensitive to any abnormal feelings) , I quickly had a seat and could feel my heart rate was increasing, I felt a little sensation like before you are going to vomit( in the back of my throat) .. (simular sensation to prior to having a siezure) . I sat down for a few minutes taking deep breaths and my pulse seem to drop back down to normal, Was a bit unerving , Any thoughts ?