Your chest aches. Food tastes like packaging. You slept ten hours and woke exhausted, or you haven't really slept in a month. You keep getting colds. You put your keys in the fridge. None of this means you're losing your mind - it means grief is not a feeling. It's a full-body event.
Your body is running an enormous, invisible program: scanning for someone who isn't coming back, bracing for a blow that already landed. That costs energy the way a fever costs energy. The exhaustion is real. The fog - "grief brain," the lost words, the missed exits - is real. The heavy limbs are real.
So feed the animal you live in, on the days you can: water, something warm, ten minutes of daylight on your face. Not as self-improvement. As maintenance for a body doing heavy labor.
And one honest caveat, said plainly because we're not doctors and don't play them here: chest pain, or symptoms that frighten you, deserve a real doctor's eyes. Grief explains a lot. Don't let it explain away everything.