Am I falling out of love with my partner, or am I sabotaging a good relationship because I’m emotionally attached to someone unavailable?

I’m F/29 and I’ve been with my partner M/30 for around a year and a half. I’m writing here because I genuinely don’t know anymore which of my feelings I can trust, and I would really appreciate perspectives from people who aren’t emotionally involved.
My partner is, objectively, an amazing person. He loves me deeply. He takes care of me, supports me, cares about my family and friends, helps enormously at home, and has made major changes and sacrifices to build a life with me. He gives me a kind of love, attention and security that I didn’t really have growing up.
We were long-distance for several months before moving in together. Strangely, not long after we started living together, something in me began changing.
I started feeling less desire for him. Our sex life became less frequent, I stopped naturally seeking physical affection as much, and over time I started feeling more like we were best friends/roommates than romantic partners. He didn’t suddenly become a bad partner. If anything, that makes this harder, because I can’t point to some obvious reason and say, “That’s why I stopped feeling it.”
For months I tried to understand what was happening. I kept wondering whether it was routine, living together, my own need for independence, stress, bad habits, lack of quality time, etc. I also felt increasingly “trapped,” despite him not actually controlling me. I started craving a life that felt more like *mine* again.
Then there’s another person.
I have a coworker I’ve known for a couple of years. We’ve always had some chemistry, but over the last several months our emotional connection and attraction became much stronger. The problem is that we were both in relationships.
We flirted, became emotionally close, and eventually crossed a physical boundary once. Afterwards we both agreed it had been a mistake and that we needed boundaries. We stopped the private/flirty communication and physical contact and tried to return to being normal coworkers.
But my feelings didn’t disappear.
I think about him far more than I should. I’m extremely attracted to him. I feel like he awakened parts of me that I didn’t even know existed. There’s a kind of tension, desire and emotional connection with him that I desperately wish I still felt with my partner.
At the same time, I KNOW this coworker is unavailable. I’m not leaving my relationship because I believe he’s waiting for me. He has his own relationship, we work together, and realistically there are many reasons why we may never be together. He has also made it clear that our “situation” hasn’t changed.
But I’m terrified that somewhere in my subconscious, hope about him is affecting the way I see my relationship.
Recently, things with my partner reached a breaking point. I finally admitted that my feelings had changed and that I couldn’t keep pretending everything was fine. It devastated him.
We initially thought we were breaking up. Then after some time apart and a lot of conversations, we decided to give ourselves until the end of the month to genuinely try again. There are no promises. We’re just trying to see whether something changes when the pressure is removed, and we’ll reassess afterwards.
And now I’m questioning EVERYTHING.
When I imagine losing my partner completely, it hurts. The idea of him leaving my life hurts enormously. Sleeping without him hurt. Looking at our old pictures makes me incredibly nostalgic. I miss what we had and sometimes desperately wish I could just “switch” my feelings back on.
But I don’t know whether I miss *him as my romantic partner*, or whether I’m grieving the loss of my safe person, my home, my best friend and the future we imagined.
My therapist recently pointed out something that has completely messed with my head.
Growing up, I didn’t receive much emotional attention or affection from my father. My partner gives me exactly those things: unconditional attention, love, reassurance, stability, care.
The coworker, on the other hand, is emotionally unavailable to me. I can never fully have him. So there’s always this feeling of waiting, hoping, wondering if someday I’ll receive what I want from him.
My therapist suggested that this dynamic may be familiar to me: one person gives me the love and safety I lacked as a child, while the other puts me back into the position of waiting for love/validation from someone unavailable.
And that scares me.
Because what if I’m throwing away a genuinely loving relationship because my brain is more activated by uncertainty and emotional unavailability?
But the opposite possibility scares me too.
What if my relationship has simply run its course, and I’m trying to force myself to love someone romantically because he is a wonderful person and because losing him is painful?
I also don’t want to reduce everything to the coworker. My desire for my partner had already started declining before things became intense with the other person. The problems in my relationship are real regardless of him.
At the same time, I can’t pretend that being attracted to someone else hasn’t complicated everything.
One thing I’ve realized through therapy is that neither man represents everything I need in a relationship. My partner gives me safety, love, care, tenderness and stability. The other person awakened desire, excitement, chemistry and parts of my personality/sexuality that I didn’t know were there.
And maybe the answer isn’t either of them. Maybe I’ve learned that I eventually need someone with whom I can have both.
But I’m terrified of making the wrong decision.
I’m scared of leaving my partner, realizing months later that I destroyed something incredibly valuable, and never getting him back.
I’m scared of staying because I’m afraid to lose him, only to hurt him even more because my romantic feelings never return.
And, if I’m completely transparent, I’m also scared that I’ll never fully get over the coworker, even though logically I know I may never be with him.
So I guess my questions are:
How do you distinguish between genuinely falling out of love and an attachment/avoidance pattern?
Can romantic feelings and desire actually come back after months of feeling disconnected?
How do you know whether you miss *the person as your partner* versus missing the safety, history and companionship they provide?
And has anyone ever experienced being intensely attached to an unavailable person while simultaneously losing attraction to a very loving, available partner?
I’m already in therapy and I’m not expecting Reddit to make this decision for me. I just desperately need perspectives from people outside my situation, especially anyone who has experienced something similar.