I can’t get over my ex

My ex and I have been broken up for 2 months now. And I just started to explore the dating world again, I’m not looking for a relationship. I just want to show myself that there are more fish in the sea. And I’ve gone on a few dates with this one guy, and he is great and I love talking with him and hanging out. But when the date is over I start thinking about my ex. And it hurts me because I want to think about the new guy, not the guy that broke my heart. Any tips for moving on?