The thought that someone doesn't love you enough is a trick of the ego. You can think of it like an optical illusion. It is a perception problem! You have a sense of lack in your mind and you seek completion in a relationship in form. You expect your partner to be there for you. But the human construct is just a paper doll. You cannot count on your perceptions or on the other person to act out what you want. The "person" is just a still image flashed many times. They will not show you your internal nature. You have to forgive your perceptual distortions.