Studying through flashcards, but I still can't remember?

I am studying American History and there are 55 terms given to students through class lectures. 10 of those terms are going to be used on the test. We do not know which terms will be given, so this is going to be a bit worry some. The test is not a multiple choice answer. It is a term given to you, and you have to explain it the best you can. Each of those terms worth 5 points, and there will be some essay question that I have to study for which will worth 50 point.. I have created 55 flash cards, but I cannot remember all of them. I can only remember atleast 30 of those terms. My head hurts because I've been studying 4 hours straight including yesterdays hours. Right now, I am a bit clueless because a few hours ago, I remembered most of those terms, and now I forgot most of them. This is a summer class I'm taking, so days are going by really quick. Test is tomorrow. Am I screwed?