Im scared

I have spent the last 20 years of my life fighting to stay alive. I feel well for a couple of months, then I crash into a deep depression. I normally end up in hospital for a while, before having another period of being OK. I will then repeat the cycle, over and over again. I have had enough, I can't go on like this any longer. I now homeschool my daughter and I can't let her down. Her whole life I have failed her and my son. They have had to watch me go through the cycle of ups and downs. It has been so hard for them. Now my daughter needs me to be there for her and I believed I could. I thought that if I was determined and focused on staying well, that I could do it. The problem is that I can feel myself going down very rapidly and I'm scared. I don't know what to do. I can't seem to be able to get hold of it. I am feeling so alone, like I am the only person in the world. I know that sounds so selfish but I just feel so empty. What can I do? I'm so scared