How to know if it is a fad or love.
Two years ago I met rob, my boyfriend's goodfriend. Rob and I had always been smitten with each other and got a long well, once a month we would call iif something was stressing us and needed advice, but we both enjoyed the hour or so call. My now fiance is out of the country and Rob was visiting in town, innocent at first but we finally realized after a week of inseperation, how much we cared and desired for each other. Despite vast distance, we have been able to see each other every other week. Each time, we become closer, talk about things we can't talk to our partners about, and sex has never been easier or more enjoyable. We feel we love each other very much, as both lovers and confidants, and have connection we don't share with our partners. We will end it soon, however we are devestated we found someone we love and relate to. Is it just a fad while our other relationships struggle? Its the most natural relationship we have had in a year, but we have longterm relationships

In most cases the initial rush of a relationship is the best, the sex is the best, the emotions are the highest, and if the relationship is illicit then even better.
But you want to define love and make sure what you got is it? Okay I will solve the riddle of love right now (LOL).
Or I will just share what I have read or believe:
“Love is not a feeling. Love is an action, an activity. . .Genuine love implies commitment and the exercise of wisdom. . . . love as the will to extend oneself for the purpose of nurturing one's own or another's spiritual growth.....true love is an act of will that often transcends ephemeral feelings of love or cathexis, it is correct to say, 'Love is as love does'.” Scott Peck.
Love is sacrifice
Love is giving to the few, or THE ONE, in ways you do not to the man.
Love is forgiveness
Love is Grace (giving when not deserved)
Love is Honesty
Love is commitment
Love is putting another needs and feelings ahead of your own.
Love is shared beliefs.