Answer: Because, to him, your pain is an inconvenience.
He sees it as you taking advantage of him, even if you’re not asking for anything. In his mind, you being sick ruins his mood, disrupts his life, and makes you less available for him.
And deep down? He may not really believe you. You’re a woman—women exaggerate. At least, that’s what he tells himself.
It’s not that he doesn’t see your suffering. It’s that he doesn’t think it matters.