I loved someone for 13 years now he dumped me. I am not able to forget him and move on.

Try surrounding yourself with people you can rely on. This can possibly fill the void of losing someone close. Also if you believe this is unfair try standing up for yourself. Not exactly in this event, as this already happened, but you can try explaining that this is unfair to whoever you think needs to hear it (preferebly not to someone whom this will cause unfixable controversy with or political controversy) as to say out loud and to assure yourself this isn’t fair. Possibly find people who were in similar situations as you and do something productive with or just talk to each other for reassurance. Know this isn’t your fault and you didn’t hurt anyone on purpose, this just happened to be an unfortunate event that was out of your power and descision. These events can be worse than others that are within someone’s power so pain is understandable as well as familiar attachement. If it helps, try to accomplish detaching yourself from him as to achieve a goal. Thinking of it this was can help you want to succeed. Good luck and I hope this helps.