Sometimes I get into the same situation as you. Do blocks on your own, focusing on one thing at a time. So, say you do 5 starts, focus on a) reaction time, b) first few steps, c) arm swing d) knee lift e) put everything together.
This will help you get your confidence back, and then you can start doing blocks against other people. When you do this though, only think about one thing, and that is just concentrating when you are in the set position for a noise. Everything else at this point should be automatic. Thinking about things only makes you slower!