Why don't I love her anymore?

Love changes as people change. You don't state how long the two of you have been together or if you are married, but in any relationship there will be times when one person will love the other more or less. If there is stress or problems this may interfere with the closeness in a relationship. Communication is the best tool and you need to learn how to sit and talk with each other, but realize that love comes and goes and it never stays the same.