Tired

I’m 20 years old and 5 classes shy of getting my diploma. Long story short, I’ve just been through a lot and ended up getting my GED when I was 18, but I felt incomplete so I went for my diploma. I want to be the best mother for my son, but it seems like every time I feel like I’m unstoppable something knocks me back down. Yesterday morning my little brother who was only 19 died in an accident. He hit a tree on the way home...the home that I promised to come visit before the summer was over. I feel like a failure. I failed my little brother and I am going to end up failing school if I don’t find some motivation through all of this. I just get so sad to the point where I don’t want to do anything....what do you guys do when you’re like this?