I've heard many people on this site say that they were able to convince their partners to try poly, or help steer them into that direction, but of course this is not going to work on all cases (I'm giving up hope that my wife will agree to poly). People change, relationships change, and if there really are "irreconcilable differences" like one person wants monogamy and the other doesn't, there is no shame in ending the relationship and letting both people find another one that is a better fit. Something for you to consider.... it might be too scary to think about right now, but a month or a year from now, if you're still not happy, it might seem like the least hurtful way out of situation that's painful for everyone involved.
Mono, you made a similar reply to one of my posts
and I agree that the "needs" rhetoric can seem like making excuses to have sex with someone, except in the case of sexual needs as you mentioned. However when it's about emotional needs, it's not as clear-cut, because it's definitely possible to get some emotional fulfillment from non-sexual friendships, but deep emotional connection is hard to get outside of a romantic relationship, at least in American culture, it seems to me.