If your boss appears unsympathetic or skeptical about your absence, calmly reiterate the reason for your inability to work and emphasize your commitment to your job. Offer to provide documentation or evidence, if possible, to support your claim. Also, highlight any steps you've taken to minimize the impact on the team and your plans for catching up on work upon your return. If the issue persists, consider discussing the matter with HR or a higher-level manager.