Have to agree with Moremi. Those are warning signs for me, too.
As for the guilt, take a serious look at the time you spend with your kids. Are you doing everyday stuff, or hiding in your room? If you want to spend more time, play a game with them after school. Something as simple as a card game or short board game will alleviate your guilt and perk up their day. Have a snack and ask them about their day. Any little thing that is interaction will be meaningful for them.

As for tired, the kids are in school, so go back to bed for a few hours and get yourself the energy to interact with them when school is over. My Mom was permanently depressed when I was in grade school. But I do remember the after school moments when we'd sit together and have a snack and just talk about my day. Those were special times for me.