Thank you for describing how I feel. :) I am 3 weeks and it's just beginning...I have a 1, 3, 4 and 6-year-old, too. My last 3 pregnancies I was on the couch almost 24/7 all day. I was tired to the point where I didn't understand how people can be pregnant and lead normal lives. I also had nausea on and off all the time. And I always get 9-10 hours of sleep, so it's not like I wasn't sleeping at night.
Maybe fatigue hits me harder than most? Now with #5, here is what I did:
1. The 3-year I put in preschool 11:45 to 4:30 every day except Monday. That way, I can get a long nap when my 1-year-old naps in the afternoon. (And the 4 and 6-year-old are both at school, too, then!). And the more they are out of the house, the less they are around a grumpy pregnant mom (which really, I feel they deserve better). Better a long school day with smiling teachers than a grumpy, tired mom at home.
2. I joined a gym with a pool and childcare and will go 3 mornings a week to exercise. I'll start the pool once I'm too uncomfy to do land stuff. I will not use pregnancy as an excuse not to exercise. So, off I go...
I always found I was least tired second trimester. And yes, we've done cereal every day throughout pregnancies or easy food. It's just trying to survive one day at a time.