Bipolar moods can swing pretty rapidly, so it is a possibility. Borderline Personality disorder is also a possibility, as people can love you one second and hate you the next. But back to the bipolar. Anger, irrationality, rage, and many other negative emotions can be seen during a manic episode, and with such rapid swinging, they actually could love you one moment and hurt you the next.

As Cocoabean said, this does not mean you have to put up with it. There is also something called a domestic violence cycle, in which the person doing the damage can be penitent and loving one minute, and in a hateful or violent state the next. Once the rage is over, there is a short time of peace, and then the cycle may begin again. A bipolar person can also be an abuser, so if this is what you are living with, don't let the bipolar be used as an excuse.