Hia,
I'd like to tell you that my daughter is very hard on herself, just like you. She has no sleep schedule and often gets no sleep, or 3 or 4 hours, and she thinks she functions fine. However, I notice when she gets little sleep she rambles about anything that comes to her mind, which is a LOT, and she makes a lot of mistakes in her speech, with her memory and with her typing. She absolutely refuses to acknowledge that she needs more sleep in order to function well. It's like she doesn't notice the difference between when she functions well, and when she doesn't.
My personal opinion is that you are being too hard on yourself. Let yourself get a healthy amount of sleep, good diet, and as well, time to just relax, and you might find that you are not troubled so much about the fear of failure. This is when you'll be in an optimal state of mind, which will help you learn more efficiently.
However, I've been there and done that, so I can sympathize.
Do consider getting good, and regular sleep though.