I want to quickly address poly as a choice or orientation: a need or a desire:
It's not an either/or, in my experience.
Some people I know absolutely cannot be poly- or be mono- and be happy.
A. Monogamy is a clear orientation for some. No amount of self-control,
Or self-work, or understanding, can make them happy with open relationships.
B. Polyamory is a clear orientation for some. No amount of self-work, self control, or understanding can make them satisfied with one partner and Mir want to look elsewhere.
C. Some of us are bi-modal. I am. I can do mono, and be satisfied. I can do poly, and be satisfied.
D. Some people are neither. They can't be happy mono, because committing to one stifles them. They also can't be happy poly.
E. Some are poly-supportive. They don't want multiple partners, but can happily support you if you are in a relationship with them and do.
And More.
Just like some people are gay, straight, bosexual, asexual, graysexual, etc.
It may be a need. It may be a choice. As a C person, it is a choice for me.
I can date A,B,C, and E people. I can't do the tension of d, nor be poly when someone is mono or mono when someone is poly. I know mixed couples who can- different orientations are not a deal breaker. And I can only date someone mono if I don't have an anchoring poly relationship. (One we intend to continue)
Where are you? Where is your husband? If enough of your your needs were met within the marriage, would you be okay being mono in behavior? If he is given the opportunity to meet your needs, and doesn't want to, or can't, is he Kay being poly?
Orientations can change. This is not static. But willingness to be open to a mode of life is a prerequisite, and may not be present.
I strongly think you should finish with your husband first before opening up. Give him an oportunity to meet your needs- and you to do any adjusting you need to meet his. Give him an opportunity to meet his own needs - and you yours. See if this marriage is with keeping, and, as a desperate question, if it is, can you and he either meet key needs or agree to have them met elsewhere.
You may want to look into swinging rather than poly, possibly.