googley - we've all been there! It does suck and I'm so sorry that you are suffering right now. As Melissa said, sometimes it helps to step back and take a break, but I also know that sometimes it doesn't. The brain won't stop racing no matter what you are doing. I know I can't function when my brain does that.

Have you talked to the professor? Perhaps he/she can offer you an extension?

I wish I had a better solution, but I don't. I can listen and offer hugs though!