Love does not hurt. Physical and/or emotional abuse are not a part of love.
Love is not manipulative, it should not be used to get others to do what you want. You should never give in to demands based on the, "You would do it if you loved me!" tactic.
Love is an intense feeling of caring for another person. It can take many different forms (romantic, friendly, familial) but it is always about caring.
Although it is true that a big part of love is putting another person's happiness ahead of your own this never includes compromising your values or being untrue to yourself.
If somebody asks you to do something that you don't want to do in order to "prove" your love they do not love you the way you might think they do. When you love another person you don't ask them to sacrifice a part of themselves in the name of that love.
It is possible to feel romantic love for more than one person at a given time. Just think, if it is possible for you to love both of your parents at the same time why would it be impossible to feel romantic love for two people at once? Don't beat yourself up emotionally if you find yourself in this unhappy situation. But be sure to remain single and be open and honest with all parties about your feelings and confusion.
Sex is NOT love. Love is NOT sex. Sex can be a part of romantic love but it is never mandatory
Romantic love can (and often does) fade. When it goes there is not always a reason. When somebody falls out of love with you it does not reflect upon your value as a person or your desirability.
Love should make you feel happy, secure and appreciated.