Men like damsels in distress. **Also, the more time they spend with a person, the more they grow on them.** That’s why he seems angry or didn’t ask about your feelings. He honestly thinks there’s no issue.
You don’t live there, and you’re not the wife. You are just the girlfriend. He can do whatever he wants without your permission. This reality has crashed into you suddenly where before you could be happy and carefree.
At his end, after a month, she should start giving him rent. That would make it a lot better.
At your end you could have him stay at your place, or stay all the time. Maybe help the girl get that apartment or set her up with some other friends temporarily. Put some furniture or a lot of your stuff there so there is suddenly no room at the inn.
For both of you, now have an agreement that no members of the opposite sex can stay over. Too much jealousy.
Though I run this site, it is not mine. It's ours. It's not about me. It's about us. Your stories and your wisdom are just as meaningful as mine. 