A very useful article about relationships with somebody suffering from Borderline Personality Disorder. If you recognize what is said in this article in your own relationship perhaps professional help is what is needed. As always avoid self diagnosis or diagnosis on others unless qualified.

Caring about someone with borderline personality disorder (BPD) tosses you on a roller coaster ride from being loved and lauded to abandoned and bashed. Having BPD is no picnic, either. You live in unbearable psychic pain most of the time, and in severe cases, on the border between reality and psychosis. Your illness distorts your perceptions, causing antagonistic behavior and making the world a perilous place. The pain and terror of abandonment and feeling unwanted can be so great that suicide feels like a better choice.

Source: Loving Someone with Borderline Personality Disorder | Psych Central