If you are referring to a romantic relationship, it would depend on whether or not you were married to the individual in which you are in a relationship. If you are not married, you should consider the reasons you are in the relationship. Why do you believe they don't love you? Maybe sitting down and having a good heart to heart would clarify some things. "I feel like you don't love me because..." or "I feel unloved when..." Those might be good places to start. It could be a number of things on their end: too busy, taking you for granted, self-centered, oblivious to how you feel, etc.
If you are married, especially if there are children involved consider this: The institution of marriage is instigated by God. Even if not done in a church, vows (promises) were made to remain together till death...not until one of us doesn't feel like it any more.
I think finding out why you believe you are not being shown love and the significant other's perspective on this would be the right place to start.