Deep vulnerability can make suffering and fragility feel like an inseparable part of life. A person might feel as though they are constantly standing on the edge of a fall, with pain following them like a relentless shadow.
The primary approach among commentators is that David is experiencing severe physical and emotional distress. He feels entirely weakened and depressed by illness and hardship, to the point where he expects to walk with a limp and fears he will be unable to rise from his bed for a long time [רד״ק, אבן עזרא, מאירי, מצודת דוד]. Beyond the physical toll, this creates a state of constant anxiety. He feels completely accustomed to failure, as if disasters and painful blows are always prepared and waiting to strike him [רש״י]. His pain never leaves his sight and remains constantly in front of him [רד״ק, שטיינזלץ].
In contrast, another interpretive layer views this suffering through a spiritual and personal lens, specifically relating to Bathsheba. Drawing on the biblical concept of a spouse being formed from a rib, this approach suggests that Bathsheba was destined and prepared for David from the six days of creation. The intense pain he experiences comes from the fact that he took her prematurely and through indirect, difficult means. In this light, his agony is not a physical illness. Instead, it is a profound emotional sorrow and a constant state of guilt over the incident involving Uriah the Hittite. He is plagued by continuous anxiety over the damage to his honor and the heavy burden of his own conscience [תורה תמימה, אלשיך, חומת אנך].