I want to give up?

I’m in a chemistry class this summer which I absolutely need to pass this summer otherwise I won’t get into my program it’s the only thing I need, I have been working the hardest I’ve ever worked in my life, working a lot, taking three classes, and moving, I study like I’ve never studied before, I had a low C still and yesterday she graded the test and I got the lowest in the class. Even with a notecard filled with things because I didn’t have enough time to take the test. They are going to drop the worst exam you have but I can’t imagine having hope for the next three weeks when I am sitting at a 68 percent. I am so depressed and completely hopeless.