I'm so sorry you are hurting so badly! You don't deserve it. PLEASE do not hurt yourself. Your kids need you. Trust me, I understand. ... But please don't.
I lost my mom when I was 10 & I stalk have a gaping hole at 46.
No matter your kids age, they need you.
I have no advice on the marriage, as mine is in shambles too.
Please contact someone IRL. And vent here. People care.