How do I move on from being cheated on and stop thinking about it?
Thank you very much for explaining your experience and current situation. These that you describe are very painful, tough and unfair circumstances and I am truly sorry that you are going through such a hard time. Besides, let me also say that I completely understand that these are your feelings regarding all that, it's completely normal that you feel devastated after what you found out. As you experienced a huge pain, it's understandable that you are concerned about the potential repetition of this eventuality.
To be able to deal with this and, eventually, move on I honestly think it's capital to clarify something regarding this situation: you must not ever blame yourself for what happened as it's not your responsibility, it was something that was not under your control. If that was the case it would have never happened. You need to actively treat and talk to yourself in a fair and healthy manner, even more now that you are facing this issue.
On the other hand, there is some work with forgiveness to be done, from my point of view. I understand why you don't feel prepared for it and I don't want to rush you at all, you need to take as much time as you need. Nevertheless, let me also clarify that forgiving wouldn't be something you need to do for him or for the relationship's sake, which are also involved for sure and would also benefit from that. When I suggest forgiveness as a possibility though, is because I truly believe that will make a difference for you in terms of breaking with the past and moving forward.
Finally, other techniques that I think can be very helpful in your case are meditation and mindfulness. When you put your attention on the present moment you are not in your thoughts. If you train your attention on an everyday basis you will be able to cope with those automatic thoughts easier. Furthermore, you will also see the effect in terms of concentrating better and being more present in your life. You can start with an easy meditation that only takes 3 minutes per day, where all you need to do is focus on your breathing and, whenever your mind goes away to your thoughts, you only need to KINDLY bring it back to the present moment.
I hope you achieve your purpose and can go over the situation. You only need to have a plan and believe in yourself and you will do it for sure. Wish you all the best.