A serious answer from teenadvice (as recommended by FBGS):-
"How can I tell I'm in love or is it just lust?", What feels like love to one person may be nothing more than attraction to another. Some people fall in and out of love quickly and often while others are never really in love as much as they are in lust. What is love? What makes you want a romantic relationship with one person and not another? How does your heart choose a partner? Why does love end? These questions can't be easily answered.
One of the most confusing quasi-love feelings is lust. Lust is a very powerful, very intense feeling of physical attraction toward another person.
Lust is mainly sexual in nature - the attraction is superficial based on instant chemistry rather than genuine caring. Usually we lust after people we do not know well, people we still feel comfortable fantasizing about. It is very common for people to confuse lust for love. But why? What is it about lust and love that make them so easy to mix up? If lust is all about sex, how can a relationship without sex be about lust? some people struggle with this because they see lust in the Biblical sense, but lust isn't that sinister. Lust is about physical attraction and acting ONLY on physical attraction. Love is about much more than that. Many adults confuse an intense attraction for some sort if divine love. Lust is clearly not love. Love is based on more than just physical attraction. Sure, attraction is a factor, but love goes deeper than that. Love is based on caring, friendship, commitment and trust. When you are in love it is as if you have your best most trusted friend at your side AND you feel physically attracted to them. It is the best of both worlds! Love is a shared feeling between two people who have a vested interest in one anothers happiness. Love is not about jealousy. It is not about conflict. It is not about testing. Love is a positive feeling. If it is tainted by mistrust, jealousy, insecurity or spitefulness it is not really love but merely a pale copy. Love is the total surrender of your heart to another person with the security of knowing they will treat it better than you will. Love should feel good. It should not feel bad. Love should make you want to be a better person, it should not lead you to do something self destructive. Love is not demanding of your spirit but lifts it and makes it glow. Love is a good thing. Anything less is lust, deep friendship or attraction. So the sappiness aside, the question remains, how can you tell you are in love?
There is no easy way to find the truth behind your feelings or the feelings of another person but there are some tell-tale signs that love is blooming (or growing deeper). If you agree with 7 of the following 9 statements you are probably in love.
-You know, because you have been told by your significant other, that your deep feelings are returned in kind.
-The object of your affections makes you feel special and good about yourself.
-If/when you feel jealous it is always fleeting; you trust your partner not to betray you or hurt your relationship.
-Nothing makes you feel as serene as when you and your partner are together.
-When you fight with your partner you usually make up within a few hours and you always agree that nothing is more important than you both being able to express your true feelings (even if they sometimes cause conflict).
-Your partner never asks you to choose between him/her and your loyalties to your family and friends - if you do choose him/her over them you always have a good reason and it is always YOUR decision, and your decision alone.
-Neither you or your partner feel the need to test the other's loyalties or feelings.
-You are more yourself when with your partner than you are with anybody else.
-If sex is part of your relationship it is by mutual desire and agreement without the slightest hint of commitment testing or persuasion.