Roller coaster seems pretty common. What I thought I should mention is that your husband may be on a roller coaster too. You didn't really say whether poly is a side of himself he's recognized all along, but he may be grappling with changing a lot of expectations and self image too. just keep talking about what both of your are feeling. As was said, it's better than hiding things, which puts up walls; the talking can help you know each other in ways you didn't expect.
And for sure, it just takes time.