Nihilistic, that can mean a few things. Break it down for me.
This is a quote from another post, which I thought might apply to your situation.
"When I am in the stage of, 'why bother, I won't make it anyway', the very next fighting thought is, why give up, I might just make it! When I was your age, I was very much stuck in that frame of mind" This person had suffered from abuse, and major depression. Years later, she is still going, doing well in spite of it all. Deals with her depression, takes good care of herself.
Remember that you are looking at this from you level of maturity, age, now, and that later on if you re-examine your beliefs, understanding, etc. of the current situation , you will see it differently. And sometimes you will see that you were on a roll of disappointment and disbelief at the time, with good reason, and it does grind to a halt eventually. There will be better times interspersed in with the not so good times of depression. I can't count the times thru my life that I felt it was too unbearable to go on. Many. And I just endured. And a good thing, because there were a lot of GREAT things that happened, although I still had trouble with recurrent depression.
Great things? I travelled to Africa twice and went on photographic safaris. What a different life. After 50, I went to Mexico a couple times, learned to snorkel and see the beautiful colored fish, made friends with some locals who were very attentive to my whims, went parasailing, lived in a foreign country for a year while my husband #1 was in the Army, gave birth twice and have 2 successful adult children now. They have not shown to be struggling as I did. I've had pets that have given me so much joy. Raised a blue and gold macaw from a featherless baby. Had a canary that lived for 9 years, serenading me at sunrise and sunset every day. My dogs adored me. Built a small fish pond and put koi in it. Planted many flower gardens that were spectacular. Good times do come to an end. Then its life as usual. And maybe bouts of depression.
Life always goes on. Don't be too quick to bail out on yourself.
Now, if you're falling asleep in class it might be because you aren't eating enough. That used to happen to me. I had toast and jelly for breakfast, donuts and milk for lunch. A very hard sugar high, and rock bottom low. Figure out something to eat, cheese and crackers, microwave soup, go have a real breakfast. You know what you can do. Do it. I don't think that its because you're tired tho I may be wrong. You're very depressed. Feed yourself good food, even if its not very much.