How do I stop thinking so much?

Hello Gwaine and thank you for asking a question here on BetterHelp. Having recurring thoughts can be really frustrating, especially when they are thoughts you're trying to avoid or thoughts that cause negative emotions. Our thoughts, emotions and behaviors are all linked, so these negative thoughts that you were having will lead to different emotions which will eventually lead to behavior change. This is why it's so important to understand why you were having the thoughts and what to do about them. I have some ideas that I think could help but I think most importantly we need to talk about therapy first. 

As I was stating our thoughts, emotions, and behaviors are all linked. When we have been dealing with negative thoughts for a long time it can lead to that behavioral change. Sometimes we don't even recognize this is happened, and sometimes we need help changing this behavior, controlling the emotions and changing the thoughts. Because of this I would recommend talking to a therapist. It's very easy to get linked with a therapist here on BetterHelp, all you have to do is click on the get started button on the main page and follow the prompts from there. You'll have to answer several questions and then you will be automatically linked with a therapist, if you don't like the therapist you are linked with you're more than welcome to choose one on your own or ask to be automatically linked to somebody else. A therapist could help you recognize behavior in your life that is toxic that you made if that was completely normal, a therapist can help you recognize barriers in your life you didn't even know existed but are stopping you from being the person you want to be, or a therapist can help you understand the root cause of your problems and help you reach solutions faster. Most importantly, they can give you coping mechanisms to help you make it through those really difficult days. I hope you will consider getting linked with somebody soon. 

if you were sitting in front of me in a therapy session right now, the first thing I would do is tell you to explain to me what these recurring thoughts are. We have thoughts and emotions because our body is trying to tell us something, trying to ignore these thoughts or push them back would be ignoring what your body is trying to tell you. We want to understand these thoughts and why they are happening, write them down, then write down any emotions you think are attached to them. You mentioned that you're anxious all the time, based off this it sounds like there's some sort of fear wrapped around these thoughts you keep having. I came to this conclusion because fear is the great driver of anxiety, without fear we don't have anxiety . So if you understand what this fear is, make an effort to take away the power the fear has over you, then we will reduce your anxiety and most likely have better control over your thoughts. Write down those thoughts you keep having also write down the fear that may be driving them.
One of the best ways you can respond to fear is by putting it in two categories: is it probable or is it possible? Something that is possible is something that we don't need to be concerned with. Let me give you an example: I live close to an international airport and regularly have airplanes flying over my home. It is technically possible that one of these planes could malfunction and crash into my home. If I were to have recurring thoughts about this like, "how would I be able to warn myself this was about to happen, do I need to change my home insurance, how would I get my family out in time, do I need to move to a new area?" The more I do this the more my anxiety will increase, my mind will take something that is merely possible and convince me that it is probable. Our brain has the ability to create a situation that has never happened, convince us that it is going to happen and then cause us to start emotionally reacting to it, it sounds so silly when you think about it and say it out loud but we do it all the time. And for you we want to control this fear, you need to regularly remind yourself that you are focusing on the possible instead of the probable. But what if your fear is something that is probable? If this is the case then you need to get prepared for it. Let me give you another example, when I started driving I was very anxious that I was going to pop a tire on the side of the road and not know how to replace it, looking like a fool trapped on the side of the road. So what I did is I practiced changing a tire in my parents driveway. I was now prepared if this ever happened, the fear was then gone. 
when we have recurring thoughts like you have been having it is extremely important to dissect them and look into them. You can't try to ignore them and pretend they aren't happening, dig into them, find out why they are happening, find out what emotions are attached to them and then make a plan of action. 
Throughout this I also want you to practice good self-care. People often confused treating yourself and self-care but they are very different. Good self-care means making smart financial decisions and preparing for the future, it means recognizing toxic behavior in your own life and making an active effort to change it, good self-care means recognizing toxic relationships and choosing to keep those people at a distance and setting boundaries with them, good self-care means taking care of your body by exercising and watching what you put into it. Take all those to heart and practice good self-care. I hope you are able to find something in here that helps and I wish you the best of luck!