Sleep issues

I just need to vent a bit. My son has always been an awful sleeper especially compared to my daughter but we had FINALLY got him to sleep from 8pm to 6-6:30am. It was pretty glorious considering he was regularly waking us closer to 4am. And then he got a cold (it was a cold, we got him tested). It all went to hell. Waking up coughing multiple times a night, almost 4 days straight of fevers. Trouble breathing through his stuffed/runny nose. Not to mention my daughter getting sick as well (though not as bad). We're all mostly better now, still occasional coughing, but the waking up at 4am has resumed and it's killing me. I can shush him back to sleep until a bit after 5, usually, but it takes me so long to fall back to sleep that I'm basically awake for the day at 4. Thankfully my husband's job doesn't start until close to noon so when he wakes up I get to nap, but again it takes me so long to fall asleep that it's never really more than an hour or an hour and a half. I HATE how my son sleeps.