I am weakened with my sigh.
The pain and suffering were getting to David Hamelech, but not for the conventional reasons. Yalkut Me’am Loez explains that David’s pain was doubled. First, he was in physical pain. There is, however, a deeper pain – one that is the result of a loss of spirituality. David lamented that as a result of his pain, he had fallen into atzvus (sadness) and anger. When a person is depressed/angry, he is unable to accept his yissurim (troubles) b’ahavah, with love. David wanted to serve Hashem amidst pain, but it was so overwhelming that he could not think properly. He was bothered only by his inability to properly accept yissurim as an expression of love from Hashem.