How can I talk to him?

I was best friends with my ex for 2 years, then we dated for a little over a year. It ended badly and we didn't talk for months. And I hated it. We recently started talking again and I don't want to stop. But my boyfriend isn't happy about it. He hates my ex and he doesn't want me to have anything to do with him. I really do care about my boyfriend. I don't want to hurt him or our relationship. But I also don't want to be completely disconnected from my ex. How can I talk to my boyfriend about this without getting in a huge fight or ruining anything?

If your new boyfriend witnessed your pain from your ex then that might be why he doesn't want him back in you life, or maybe according to the stories you told him. The most important person here is your boyfriend, but your ex if he was your close friend is important too. So i suggest that you explain to your ex the situation and ask him to give you time while your boyfriend gets to trust your friendship. If his intentions are just to be your friend and not to win you back he will understand and respect your wishes and maybe when your boyfriend sees that he is no harm, maybe he can trust him with you. Your boyfriend might also be threatened by this guy, I would be, so understand him and limit your communication with you ex. Good luck.