This is my first real relationship and I can't help but feel that I've missed out on a part of myself because of it.

FOMO, particularly when you're young and at your attractive/horny peak, isn't unusual. I definitely felt this way in my first long term relationship (only two years at the time). But it does cut both ways. Moving away from an SO can create the same sense of indecision, frustration, and longing. Not being able to have it all is something young people struggle with.

Recently I've been coming to realize that monogamy has never sat right with me, but when I brought this up to him he immediately shut it down and made a comment about poly people just wanting to cheat.

That's not an unfair take, given my anecdotal experience. I've seen more than one divorce start with "let's just open up the relationship". If he's got personal experience with this (family or friends or a prior SO who broke up this way) the anxiety isn't unusual.

At some level, you have to seriously ask yourself the question of who you want to spend your time with. You can't cling to an old SO while juggling a new romance, particularly if the two people in your aspiring poly relationship don't want to be together.

Cause that's what this really boils down to. Not who you fuck, but who you come home to.

On the plus side, if you're young and you are still experimenting with your feelings, you've got time to make the wrong decision and recover.

On the negative side, experimenting can be painful no matter which way you go. Ultimately, you have to recognize that other people have their own needs, and being in a relationship isn't just about what you want. Whether that draws you together or breaks you apart is contingent on compatibility. But trying to split your time and your love between people who don't share those feelings with one another is dangerous and difficult, and prone to leave everyone feeling badly.

Relationship stuff is tough, but you'll figure it out!

Hi, I'm experienced in polyamory and have been in many long term relationships, so if you do want some advice, I'm happy to try to help out. Also there is a polyamory comm, it's kinda inactive, I need to get back to trying to build it back up again soon but I've been buried under life lately so...yeah

Otherwise...yeah this kind of scenario is pretty common I find with very long term relationships as they change and grow and ebb and flow.

from a completely selfish point of view not yours at all it sounds like you want to treat your current relationship as a learning experience which immediately demotes your current partner to ex.

that should upset them unless they want you to leave.

if your need for existential growth through life experiences includes physical and emotional intimacy with someone else and don't want to burn the current bridge you must express some kind of adult honest communication and expect the worst.

otherwise just do what you want which is also quite common.

yeah trying to turn a strictly monogamous relationship poly is a lot of effort and heartache if your partner isn't wired the same way

Yeah. I get this train of thought. I’ve been with my wife for 12 years. She is my soul mate and I’ll never ever let her go. However, I felt like I lost a lot of chances to date in my life because she was practically my first real relationship. For us, poly was the correct answer though as she had no qualms being just an instrument in the band. And now I’m with my wife and my fiance of two years and it’s been one hell of a ride I wouldn’t give up for anything.

That being said, when it boils down to it, considering that your boyfriend seems very clearly against it on grounds that are based in ignorance, perhaps you can educate a little to see if he will be more amicable towards what polyamory is actually about. However, if he’s too hostile towards the idea, then you’re going to have to play by his rules so to speak. When it comes to relationships, it is indeed a work of art between two people. Both need to be working in tandem for it to be a masterpiece.