My fiance doesn't like it when I hang out with my best friend: Advice?

So my and my partner have been together for over 7 years now, we have a child together and another one due next week. We have always had a bit of a rocky relationship, but when we get along, it’s amazing. He has recently decided he doesn’t like my best friend, so every time I’m planning to do something with her and our kids, I get “in trouble”. For example me, her, and our kids went to the park yesterday, and it has resulted in him saying I choose her over him, and he has now moved our house, yet it is meant ok for him to go to his friend’s house. Tonight? It hurts me most because he and my friend used to get on so well, and now he’s decided he doesn’t like her. I always make sure to time for him too, but the hurt and stress he is causing me over something so ridiculous is just too much anymore, I can’t cope with it and cant even speak to my friend about it as I dont want her to think its all her fault.

That’s a red flag to me. He should encourage you to have other relationships