Spouse refuses to help!

I have severe ADHD.   I am the mother of 3 children. 2 out of the 3 have ADHD. My oldest is 19 and disabled. He has ADHD/Bipolar/Developmental delay/Learning disabled/ODD. My daughter does not have anything.  My youngest is 8 with just ADHD.  I need help. Im trying my best to manage mine with meds, therapy, coaching. I am responsible for helping manage my sons. So I have 3 people I am trying to help manage. MY problem is my husband. Even though he knows my difficulties, He refuses to help or be of support in any way. I am responsible for everything! Im responsible for all the financial aspects, I am responsible for all the household chores including all the yardwork.  All the cleaning, cooking, groceries,  bills, dr appts., homeschooling,   everything is on my lap! And I am struggling BIG TIME!!  Actually Im sinking! I ask him to be supportive and help me out and he refuses. He tells me Im the wife and the mother its all my job. According to him, his ONLY job is to go to work. He is home by 4 or 5pm everyday Mon-FRi and is off everyweekend. He goes to his room and watches tv the rest of the day.  But yet he refuses to pitch in at all.   How am I suppose to handle all this? Im really trying different ways to do things and mange everything but nothing is working except me sinking further and further down.  My therapist just keeps saying all this is too much for me to handle alone and that I should get some help. HOW?  What else can I do? He even refuses to let  our son read him a book because he says his schooling is my responsiblity.  Please any advice appreciated!!!