like the title says..... does any one know what the heck is happening in this drama?

SPOILER...  The reason they show the three's past is because the three's past lives were intertwined. To the end of the drama, the male lead says (SPOILER) a person whose blood is sweet to a vampire has something to do with fate (i think that's what it said not accurate...). So Don't worry just keep watching the drama it will all make sense later...