Boyfriend is insecure. What do I do?

My boyfriend and I have been going out for about six months. He’s been the best partner I’ve ever had, and he said I was the best he’s ever had and he doesn’t wanna lose me.

That being said, he’s had a really shitty past in relationships: one tried to get him arrested, and one cheated on him. I understand the insecurity he has about us, but he’s also always scared I’m “losing interest” or “thinking of breaking up.”

I can’t begin to explain how wrong this is, and I’ve explained this to him tons. I’ve reassured him plenty of times, I’ve comforted him in times I didn’t need to, I’ve protected him, and I’m always really touchy with him to make sure I’m showing interest. I don’t know how it might appear that I’m losing interest. Im wondering how I can comfort and reassure him more about these insecurities? Maybe I should bring up a discussion about this and just try and talk it out? Honestly I don’t know. He’s the best thing that has ever happened to me, but I just want him to feel as stable in this relationship as I do. What should I do?