So he is my first lover, and relationship, and these are added factors that complicate things.
I sympathize. It can be hard to feel strong feelings the first time out in your first adult relationship. Everything is VERY vivid and loud in feeling. Haven't gone this road before, so all of it can seem weirdly INTENSE.
The bright side IS that it is all new and it's a freshness felt not just on the level of this one relationship but in your current stage of life.
There can be other lovers, other New Relationship Energy times... but it's not like the one that is the first one.
That said? You do not sound like you are monoamorous and ok polyshipping. You sounds like you are monoamorous and monogamous. Is that so? You experimented and came to reaffirm that core value in yourself?
Well... you do not have to spend your whole life with your first lover -- life is long. A good sex share is a good sex share and can be lovely and all kinds of wonderful in mind, heart, body, and soul. It can also be a fun roll in the sack. There is spectrum there.
Do not make major life choices based on sex alone -- like staying in a polyship where you love the shared hinge but do not love the polyship shape. Sex can be part of a loving relationship, but a loving relationship is more than just sex. Do not square peg round hole yourself to a place of intolerable. That's not health.
Poly thing IS a big compatability issue. What you feel for him does not change and does not have to. But your BEHAVIOR might have to change. You can continue to love him even if you break up because you want a monoship and he cannot provide this with his wiring. You cannot provide polyship with your inner wiring either. It is what it is. Nobody's fault. Be friends. Do friend behaviors now instead of GF behaviors. Be attached. Be loving. Share friend love instead.
Free yourself to have a romance ALSO in the shape that you can thrive in. You do not have to "lose him" from your life just because he can't do a monogamous romance and you can't do a poly one. It's a personal limitation reached. So it is.
There's always gonna be a first time for everything. It is special to have shared that lovership with him. That is good, and the experience was worthwhile. Could enjoy it for what it is.
Cada epoca tiene su encanto.
Every age and stage has its charms.
Enjoy the life experiences of your age and stage. The sweet AND the bittersweet. Nobody has done anything wrong here -- and it is totally ok to accept that things just are what they are.
I could be perceiving things wrong in thinking that you lead toward breaking up and have trouble digesting that.
It could be that you may be thinking about it the other way -- about a major core value/belief change within. It's possible, but would you be changing it just to be with him or for YOU because your belief base is having a paradigm shift all on its own? Would you change it even broken up?
Which way are you leaning here exactly?
How can people best support you at this time? I'm willing to be supportive but I'm not sure where it is you are at or aiming for here. Are your needs just basically a safe place to vent and find comfort at this time while you are coming to terms within?