I can't stop thinking about my ex. What should I do?

maybe you still have feelings sit them down and talk about it and explain why it is you are thinking about them and try to find solutions

Well, for one, don't force yourself not to think about them. Chances are that will only make you think of them more and miss them. Also, remember that it's okay to miss someone you were once in love with, in fact it's very normal and even healthy, depending on the severity. If you feel as if you are still in love with the person and can talk about why you broke up in the first place and resolve it, maybe there is still something there. A lot of people breakup due to just lack of communicating. But also, you may just miss them. Just like when people chose to move to a different state. Yes, they will probably miss their old home, but only at a distance. It does not have to effect you and disrupt your life. Maybe you should remain friendly with your ex and just see how they are doing. Keep the friendship or even just let them know you still care about them. You loved them once, so there is nothing wrong with still caring about them and wondering how they are doing.

Then, think about him/her. make a list of the things that you liked and hated/disliked about him/her. The list would help you decide whether he/she is worthy to be thought about.

The best things would be if you can find a healthy alternative thing to think about. Like I looked for different sports and made a few new friends. So if my mind thinks about my ex I have an re-direct procedure.

Try going out for exercise or try a hobby that will take up most of your time. Soon enough, her thoughts will escape the building

Have so time for yourself. Remember that you have friends who can help you. Have a girls night out or boys night out. You need a time to yourself from all the mix feeling. Take a vacation or just do something fun you like