This Feelings's Unpredictable

i have a word. easy. an easy word to figure out. this word is famous. everyone has this word in their life. this word blend in a day life, among family, friends and lovers. this word makes your heart skip a beat, makes your head spinning around, makes your lips can't stop smiling, makes 'the butterflies' coming and fly inside your stomach. but, it hurts too. it's just rubbish when you don't need it. it just a word you can find in dictionary. a word which comes like a ghost in the dark foggy night and blind your eyes a while and it makes you feel uneasy sometimes. could you give me a clue for this? yeah, my feelings truly unpredictable for few days just because this suck word and i hate i could have this word to describe my whole feelings right now.