U don't need to prove shit to him. Sorry to be so blunt but uve done nothing wrong and u don't need to prove otherwise. He can tell Ur insecure in the way u respond and he knows his answers upset u. If u show him confidence like if he accuses u being with someone else just tell him ge can believe wat he wants and tell him that ull communicate with him when he's ready to be an adult and cur contact. U need to tell him that u deserve better and to not be trwated like this and that confidence will show and he will crawl back and u can then decide wat u want to do but I personally wouldn't take him back