What do you do when you're supposed to be in love with your boyfriend but you're having real pangs for someone else? It's a horrible situation accentuated by the total unwillingness of that 'other' person to pursue (or continue actually) something passionate.... 
I feel disgusting, cheated, cheating, humiliated, ridiculous, and so on (figure out the rest).
Or...
Don't say a word to your boy about it until you're really sure that you actually deep down know that you just don't love him anymore but it's nothing he did and there's nothing really he could have done different, that it's just time that brought you to where you were.