Have you tried pre marital counseling?

What's lacking in your relationship that you are making new emotional connections with other men? In so far as to discuss sex with someone else?

Worth exploring in individual therapy as well.

Could very well be nothing at all about the relationship itself? It could be there's something about your sense of self that needs addressing. Some sense of fulfillment or discovered purpose in your self that needs attention? Could be a myriad of things. Seeking male companions while engaged seems like a slippery slope.