Since it happened, it will leave a clue. You can look at it from WeChat friends, if you don't delete each other after breaking up. You can also ask his same-sex friends, because same-sex friends should know more about his ex-girlfriend, whether it is his ex-girlfriend or his current girlfriend. Now that we broke up, it's a thing of the past. Cherish the present. If you care too much about his past, you may become his ex-girlfriend.
Really help you, if satisfied, please adopt! thank you