So I had top surgery 5 years ago but instantly regretted it. I swept that regret under the carpet until I detransitioned 10 months ago. So now I want new breasts, aka reconstruction. When it comes to the dysphoria aspect for me, I differ from both the mtf and the ftm experiences. Cause I want (specific) traits of both sexes, and because of that passing as my female gender is of low priority for me.
But other than that, I don't think my reasons differ much from others who replied/commented in this thread. Although I have a slew of reasons, most of them can be lumped up into these 4 different categories:
1. Looks
Basically for my body to look as I'd call it "harmonically female" from neck down. I feel like my chest doesn't fit the rest of my body which is otherwise very curvy, that most feminine clothes don't fit right with a flat chest, etc. As for size, I feel very right and comfortable with the size of my breast forms that fit nicely in a 34D and if I could get my reconstructed boobs to roughly that size (C-DD), that would be great, but I'm not too picky. My pre-op size was 32B.
2. Sensation
This one's hard to explain but touching my flat chest, feeling tight fabric on it, etc, just feels wrong and icky. And I miss the senation of boobs, soft, squishy, warm boobs. I've never had erotic sensation in that area of my body (also pre-op), but it's still an important aspect for me to be able to have boobs again to include in my sex life.
3. Sexuality
This category overlaps both points 2 and 4, but too separate to put into either. About me being a lesbian, that I want for my body to look and feel (more) similar to a partner's body. That's not really sexual, but has more to do with a deeper kind of intimate mental/romantic connection to another female cause of both being female and loving each other. Not having the boob aspect of femaleness to connect with an intimate/romantic partner does feel painful for me.
4. Dysphoria
Put simply: Most other women have breasts while I don't. It makes me jealous, and it hurts, that I don't have that very female thing on my body anymore. Cause now that I finally love being a woman, my body feels wrong without boobs to go with all the other female parts that I got from nature and still have.
And in my complicated detrans case:
I really do like having my male secondary sex traits such as beard and deep voice, that I got from my years on T, but only as additions to my otherwise female body. I don't want to lose any of my fem bits and I want what's lost back. But I feel the same about my male traits, that I don't want to lose them either. Male or female; they're all parts of what's simply me.
The way I view myself is as a masculinised woman, and my masculinity feels just as right and comforting to me as my femininity does, and I simply need and love both. But basically I feel a strong need to look totally female from neck down, which is, after all, some 90% of my body, no matter how much I want for my whole head to appear male.
And then I just have to bite the bullet that my reality is: I won't pass as female no matter how real and how big my tiddies are.
So in that aspect, my dysphoria is different, and even I don't know what it really means, cause I don't see myself as nonbinary. I'm just a different kind of woman. A bit more spicy and gnc. Because I see my gender as aligned with my bio sex I don't see myself as completely trans, but because I am still happy with most of my ftm transition, I also don't see myself as completely cis. But then I also see detrans as kind of a sub-category of trans.