Toddler mum burnout — when did you admit you needed a break?

I love my 2-year-old more than anything. And I am completely burnt out. I'm a SAHM and by 4pm every day I feel like I have nothing left. Short fuse, crying in the shower, dreading the morning. Husband is supportive but works long hours and I don't want to make him feel guilty. When did you recognise this as more than just 'tired mum'? What did you do about it? I'm afraid of seeming ungrateful — I wanted this so badly — but I think I'm disappearing as a person.