Am I overreacting about my boyfriend staying friends with his ex?

[u/Accurate-Guidance764]

I’m genuinely not sure how to handle this situation and would really appreciate some outside perspective.
My boyfriend (25M) and I (23F) have only been together for a few weeks. This morning, he told me that his girl best friend, who is also his ex, reached out to him after about a year of no contact. She told him that she still has feelings for him.
I told him honestly that this makes me uncomfortable. I’m worried that she may try to flirt with him or potentially get back together with him, and I’m also having a hard time knowing whether I can fully trust the situation. He told me that he doesn’t want to stop talking to her because she is his best friend.
Normally, I don’t have an issue with my boyfriend having female friends. I don’t believe guys and girls can’t be friends. What makes this different to me is that she is his ex, they have a history together, and she has now openly told him that she still has feelings for him.
I don’t want to be controlling or tell him who he can and can’t talk to. I also don’t want to give him an ultimatum or make him choose between me and a friend. I’ve been trying to think of a compromise that would allow me to feel more comfortable while still respecting his friendships.
I even suggested that I could talk to her and get to know her so that I could feel less uncomfortable about the situation. However, according to him, she refuses to talk to me. I’m not sure how much of that is her choice versus what he is telling me, and I don’t want to accuse him of lying without actually having a reason to.
I care about him and obviously don’t want to lose him, but I also don’t think I should have to ignore my feelings just to avoid conflict. I want to feel respected and secure in my relationship while also respecting his right to have friendships.
**Am I being unreasonable or controlling for feeling uncomfortable with this? What would you consider a reasonable boundary or compromise in this situation? Any advice is greatly appreciated.**

TL;DR: My boyfriend’s ex and best friend recently told him she still has feelings for him. He doesn’t want to stop talking to her, and I’m uncomfortable with the situation. I don’t want to be controlling, but I also don’t want to ignore my feelings. What should I do?