How to care for myself when there is nothing left to give

I have two autistic children and my husband is also autistic and has severe depression. Caring for my children is a given, it's normal and natural. Yes, their support needs are higher than your average child but it's to be expected. But my husband, well it's frustrating. I understand and accept depression is an illness. I don't blame him at all. But I'm so worn out, tired and have no space for myself. He stays in bed playing games most the day. I do all the cooking, cleaning, organising. We home educate as that's what the boys need, and we don't do much in that regard at the moment, but I do it all. I'm studying which is my me-time but the pressure of assignments is pretty stressful. There is no answer, no magic solution. But yet, I am left here, alone, isolated and with all of the responsibility. It isn't fair.