Finally had the conversation with my wife
I told her I think I have depression. Not just general stress or dad fatigue, but like actual depression that's been going on for almost a year. She cried, asked why I didn't tell her sooner, and then we made an appointment with my doctor for next week. It felt terrifying but also like I took off a backpack I've been wearing forever. Not fixed obviously but feels like at least we're doing something about it instead of me just white-knuckling through every day.
Getting professional help next? That year of suffering privately is rough. A therapist can help you actually sort through what's causing it instead of just white-knuckling through each day.
the 'why didn't you tell me sooner' response is love. she's not mad at you, she's mad she couldn't help when you needed it. You just gave her the chance to be there. That's good for both of you.