I’m poly and I’m married. My husband isn’t poly but is ok with me being poly. I started dating this girl and he once mentioned maybe down the line that he might get feelings for her one day and I freaked out. I don’t want to be hypocritical but I don’t want him having feelings for anyone else but me. He’s mono and if he gets feelings for someone else that makes me feel like I’m not enough for him. Is this weird? Please help. He feels like I don’t know what I want but that’s not true.
In the general case, I’d say that yes, wanting to be able to date other people but not wanting your partner to have that freedom isn’t fair or sustainable.
I think based on your wording that your issue here is a sort of logic problem: if your husband identifies as mono, then that means he can only love one person at a time. Therefore, if he develops feelings for someone else, that threatens his feelings for you.
But if you let go of this expectation that your husband’s identity is fixed forever, and that it has such far-reaching implications, it might be a lot easier for you to understand his growing feelings for this new person. You yourself fully understand that it’s possible to have a relationship with another person without any threat to your feelings for your husband.
Your husband may identify as mono in general, but it’s no surprise that he might be developing feelings for the person you’ve become intimately involved with. Clearly she has a lot in common with the person he already loves!
Do some introspection and try to determine what’s so important to you about maintaining the poly/mono dynamic you currently have, and try to work through some of your own expectations or preferences. I think it could be an awesome and beautiful thing if your husband saw you practicing healthy, fulfilling polyamory and was able to find himself open to trying it!