I was an unwilling Onc recruit when I started out, too. I know it's a little more terrifying than some other specialties because our patients can be so sick. But like Orange Tree said, you're new and it's normal to feel anxious. Are you being oriented still or are you on your own?
If you're being oriented, ask questions of your preceptor. Ask them what you need to chart on a daily basis and write it down--perhaps on the back of your name tag or somewhere accessible on every shift. This is how I survived my first few months of nursing until I knew everything that was expected of me. I would run down the list, check all my charting and make sure everything was in every night before end of shift. As you're going throughout the day, have different sheets of paper for each of your patients and write down things that you do for them / that you need to chart / that are important to their care (ex: Mrs. Smith is concerned about not having X medication ordered and wants you to call the doc).
If you're having issues with organization, sometimes it helps me to write down orders by hand. I'll look at the order set and put it down on paper in a certain format so that I know where to find info when I need it.
If you're not being oriented, ask questions whenever you're worried. I know this is hard because you probably feel like a pain in the a**, but it's the only way to learn and it's how to keep yourself and your patients safe. Don't be bullied into being silent. You have a right to feel comfortable at work and supported by your coworkers.
As far as patient deaths/downtrending, that is an unfortunate reality of oncology nursing. If you're religious, lean heavy on your faith. Do you have other nurses who are friends of yours? Talk to them about things that bother you. If not, you can always PM me anytime. I saw things in onc that blew my mind and had it not been for having friends to talk with them about, I would've ended up on inpatient psych!
Nights are such a challenge. I LIKE nights, but I still have issues with feeling normal when I'm on nights. It's hard to have a normal schedule of any kind when you're up all night, but there are techniques that can help you function. If you need to do something on normal business hours, try to schedule it for later in the afternoon or early in the morning. If you have to be up during the day, try to nap in the wee hours of the morning and trick your body into being awake.
Keep in touch and hang in there! Let us know if you have more questions, and as always, feel free to PM me.