Butterflies
That feeling you get that tells you you are in love. The feeling you get even just by looking at someone and your heart beats a million times a minute and all you can think about is being with him forever.
Example:
As Alex kissed her on the cheek and whispered I love you in her ear, Karen's stomach fluttered with butterflies.
As Alex kissed her on the cheek and whispered I love you in her ear, Karen's stomach fluttered with butterflies.