@Allyson
I am sharing this with the best intentions. If any of these help, good on. If they don't help, you have my permission to completely ignore them.
1. If you are religious: Pray! I'm serious. Many people may scoff at this but it truly helps. No matter your religion, it helps to shift the weight to someone else. If you are a Christian, you have the perfect guy in Jesus. If you are an atheist, please move on to step two.
2. Talk to friends: This is actually in keeping with the same idea as #1. Talking to friends will help you transfer some of the stress and weight to someone else. Let me put it to you this way: A friend doesn't actually have to do anything. They should be able to simply sit there and listen. If asked a question they will respond, if not, they will give you a shoulder to cry on. This will help. (If you're not comfortable talking about these topics exactly with them, I would highly suggest you still sit down and talk. It is good to keep your mind from dwelling on dark thoughts like these.) If you don't have any good friends, move to step three.
3. Write: I don't mean that you should write on Prose or any other social media platforms. I mean that you should write in a private notebook or in a document on a private computer. This should be a place for you to literally get thoughts out of your head. Think of it this way: The paper has to hold the weight of the ideas, your mind does not. If you don't have a notebook to write in, grab a piece of scrap paper and jot your thoughts on it.
All of these are meant to help you from dwelling on one circling thought. If you can't get the thoughts out with prayer, talk to a close friend who won't judge you based on your darkest thoughts and fears. If you don't have a friend, write your thoughts down. I have never known a piece of paper to hold any grudge or talk poorly about me. Sometimes writing is the best thing you can do!
#4 is perhaps the hardest to hear, and possibly the one that will get the best results. (Rubbing alcohol burns when you put it in a cut, but it cleans the wound.) Also let me note: all of these revolve around the idea of not dwelling on these thoughts. It's not healthy!
4. Go to a psychiatrist: The least personal and the most expensive. I think this one is an "in case all other means fail". Best friends are best for a reason. And remember, there are always people in this world who love you. You are not going unnoticed, your actions do, and will, change the future.
Life is precious, no matter how weird it can get.