Hi I've been going out happily with my partner for nearly two years now. I don't want to break up with them and I love them dearly but I'm really not comfortable with a monogamous relationship. I've always felt attraction to more than one person at a time but I've never really been open about that sort of thing with my partner. (my past relationships didn't really end well as they've either been assholes or barely of note)
I've broached the subject with them prior under the guise of some of my friends being poly & they've gone something along the lines of "I don't mind it but its not for me". I don't want to make them uncomfortable but its starting to nag on me. Once again I love them with all my heart and I definitely don't wanna break up with them to find a more comfortable relationship structure.
Any advice?

Talk to them about it and then if they're not ok, which would be
fine because let's face it polyamory isn't particularly fulfilling in the long run (watch world class psychologists like Dr K on twitch/youtube), you're probably better off breaking up with them unless staying with only them is a sacrifice you're willing to make