OK, first of all: yes, this is normal! Everyone is university, especially in the natural sciences depending on experiments/ programming/ .... knows this, because one small mistake can render hours of effort useless. You're not alone in this. Second of all: don't panic. I know it sounds ridiculous, but thinking clearly is the only thing that is going to help right now.
It's obvious your situation is unbearable to you right now, so you need to change something. Consider your options:
- Quitting. Is it worth it to quit, after you put in so much work? Aren't you going to regret it? Would research in a different place be more successful? Veering away from grad school entirely: do you have realistic job opportunities in the field you're in? And could you move back to a place where you're happier/ have more social interaction?
- Continuing. Talk to your PI. Ask for help if possible. Make a tight schedule and stick to it, including studying. It might consume even more of your time, but getting in the studying every day is going to lower your stress levels over the looming exam. Also, you must have one person you feel comfortable enough with to go out and grab a beer. Even being in a lively, more relaxed and less lab-related environment can make you feel better because you will (unconsciously) realize that there's a life outside of the lab, even though that's what yours is focused on right now.
Good luck in making your choice and hang in there. As we say where I'm from: het komt allemaal wel op z'n pootjes terecht. (Sadly there's no adequate translation, but it's something along the lines of 'It will land on its feet' - the way a cat does.)