So exhausted

Before I start.... yes I'm complaining but sometimes complaining to strangers is all you need so hear me. I do love my family so very much, I do absolutely love them. And I did anticipate some level of exhaustion but this is beyond what I thought possible in a human being so yep. I feel guilty complaining because I do love my family more than life itself but here I am.

I am so tired. I am exhausted right to the core both physically and emotionally. I work all day from early morning to early evening, then I get home and I help out at home, I don't sit down until late at night. I feel bad for complaining because my partner is home with our three week old and three year old all day, every day and that is exhausting too, we aren't making comparisons. I am just so tired. I am exhausted. I'm working myself to the ground each day and then coming home to do more work and then not sleeping at night time because of said child/infant (perfectly reasonable).
I feel like I can barely hold it together for much longer because I'm so just exhausted, needing to work and run a business to feed my family and pay the rent but barely functioning due to complete exhaustion. The novelty of having a younger sibling to our three year old has worn off and he's perhaps not getting enough attention (oops) and chucking regular tantrums that result in biting or kicking and I just can't. I love them all so much but I'm ruined at the moment. I want to spend time with them after work and be happy dad, but how can I when I'm exhausted down to my bones.