Focus on the way you feel when you are with your significant other. If you are still in love with him, you will smile when you are together and you will cherish the time you have with him.
Consider your thoughts about her. When you love a person, you will think about her a lot. The majority of your thoughts will be positive thoughts if you are in love.
Think about your reaction to his quirks. Tolerating or even enjoying some of his unusual or irritating habits is a sign that your relationship is worth continuing because the love is still there.
Pay attention to the things you say about her to other people. If you find yourself saying more negative things about her than positive things, that is a pretty sure sign that at least some of the love is gone.
Reflect on your desire to be with him. If time away from him seems like torture, you still love him. On the other hand, if you count down the minutes to solitude because you find that you enjoy being alone more than you like being with him, it may be time to leave the relationship for a simple friendship.
Determine if you are questioning your love for her because of an argument. If you think that you are, it may be best to calm down before you decide what you want to do about your relationship.