I have a partner. We've known each other for a long time and have discussed that I am poly and that I am interested in having multiple partners.

At first he was not okay with it. And then he came around to the idea and said he was fine with it because he loves me for who I am and he still gets to be with me. But then when I started talking to my other interest he flipped out and said he wasn't okay with it.

After he calmed down he says he's fine with it. But then again when I talk to my other interest (not yet a partner, but also aware of the situation) he freaks out again.

I have conflicting feelings now towards our relationship after the way he acted in this situation. He claimed that he specifically didn't like this person and that's all it was. But it makes me think if I ever have another relationship in the future he'd act the same way to the secondary partner.