Burnout is real and I'm in it

What I'm dealing with:

• 50+ hour weeks at work
• Two kids (8 and 5)
• Trying to be present and helpful at home
• Haven't slept well in months
• Snapped at my kids twice this week over stupid stuff
• Can't remember the last time I did something for myself

My manager wants me to take on another project. I want to say no but we're trying to save for a house down payment. Feels like I'm choosing between my family and my mental health. Anyone been here?