Shane knows that, knows he is a terrible patient, which is why he has been grateful for the several years that Ilya has never been around him when he's been sick. During the season, he would play it off, push through, take medicine and make it work. If he got sick in the offseason, he would bury himself in bed until it wore off, sleep it off. Now? He's married, and it's the beginning of the off season, and he's exhausted, but there's more than that.
He's finding it hard to breathe, less an injury and just congestion, and burrowing under blankets is far more comfortable than Ilya's demands that he sits up, drinks water or soup, both of which are only making him nauseous. It's the flu, probably, but he's not going to the doctor, because that would involve leaving the comfort of their bed (that he has practically commandeered, in his sweat drenched state, wrapping all the blankets around himself and hiding beneath them), and he isn't willing to do that. "Shut up." Words murmured from beneath the bedding, because he doesn't want to admit that Ilya is truthful, but he's feverish, and tired, and he doesn't need caring for (he does, dehydrated and sick). "Just let me sleep. I'm not hungry." He's not, but he probably should be, if he wasn't fighting a fever.