Hear, O YHWH, when I cry with my voice,
Have mercy also on me, and answer me.
In this second part of the Psalm it appears as though his family have cast him off, with the result that he is concerned lest YHWH too cast him off. It is necessary here to remember the closeness of family ties in Israel, and their importance. To be cast off from the family was to be rejected by the tribe. And that could be seen as being cut off from God. Such a situation may have resulted from false information having been laid against David by Saul, so that even his family withdrew their support from him. but whatever it was it went very deep.
And so he cries to YHWH that He will hear his voice, and will in compassion answer him, and be gracious to him.