You have needs and desires that want to be fulfilled. Every day they come up in dozens of ways and make you hungry, sleepy, horny, lonely. Every one of us feels needy and wants to be loved, and that's ok. It's how we grow up and how we form bonds and relationships.
The downside to growing up in such a way though, is the asymmetrical relationships that can form; only getting your needs and desires fulfilled in certain situations or from certain people; friends, family, lovers. It gets you easily attached, addicted, and can become unsustainable in the long-term, as you try to compensate and stretch yourself for the other person to fulfill your needs, even if they can't or don't want to.
As you try to find comfort and love in everyone BUT yourself, your relationship become unstable, but loving yourself is probably the harder thing to do for most people. We are not taught to love ourselves, be fulfilled with ourselves, accept our mistakes and shortcomings, as our society and culture does not accept either. Our parents tell us they love us for who we are, but out there in the real world, nobody does. Out there we need to perform and become actors, deceiving society that we fit in, running in the hamster wheel until we drop dead.
Not being fulfilled by yourself, not loving yourself, makes life more unbearable than it needs to be. It's not easy, but it gives you freedom and power over your relationships and your life, not being dependent on them, but enjoying them for what they are.
Can you love yourself? Can you be fulfilled with yourself? Take care of your own needs and desires? If the answer is no, or there is a hint of doubt, go deeper. Follow that feeling and find out why. What is it that you are insecure about? Are you scared of your partner's love fading? Your partner no longer giving you the attention and love that you crave? Or are you unhappy with yourself? Maybe you are uncomfortable with your body image, or you have unhealthy habits that you are ashamed of.
Go deeper and ask yourself where they are coming from? Some trauma in the past? Or the idea that you have to be perfect, else nobody would love you? Try to reach the origin of your insecurity. Understand it, accept it, and find the desire to be loved hidden inside it. If you can, then you have found a way to heal, to accept yourself. Make good use of it.