Fat experiences

I've been into feedism and weight gain ever since I was a teenager. It wasn't until some years ago that I realized and accepted that it also involved my self gaining weight. I actively started to fatten myself up. My (at the time) wife did seem a bit concerned but she didn't harass me about it. She knew about my interests and what I did online. I didn't find out until some time later that she thought it was just some kind of phase.
After a while, I was getting pretty chubby with a fairly pronounced belly. One night as we were kissing, I placed her hands on my belly. She pulled them back only for me to put them back on my belly. I then told her that I liked it. She smiled and asked "you like being the one with the belly?" I said yes and then watched as her face turned from a smile into complete horror (we were both kinda stoned at the time so that might have fueled her reaction a bit). My heart sank as she proceeded to have a break down.
We've since then divorced. Not because of this incident but I believe that my interests had a part to play in it.

Oof. This is brutal.

This is the best fetish ever when it works out. But it's also the worst fetish ever when it doesn't work out. It almost always doesn't work out.

Yup. You feel embarrassed and you get that self conscious feeling because you've exposed yourself and got rejected. In this case, rejected baddly.
I wish it would work out more often than not

Me too my friend. Me too. It's literally one of the worst feelings possible. The trauma is so deep I still have a hard time opening up fully to my ravenously obsessed feedee girlfriend of 4 years who recently said she wants to gain a lot of weight.

You ever expose your truth to a partner you trust, get rejected, and then they tell everyone else and suddenly you stop getting calls from friend groups and people at school look at you weird now because everyone knows you think your friend's mom who is 600 pounds is a living goddess? now that's some shit.

Well, my ex didn't tell anyone (as far as I know). Even if she did, it wouldn't have really changed anything for me. The friends I thought I had here we're her friends and they stopped talking to me after the divorce.
Though I can't imagine the embarrassment that you felt. That's horrible. Friggen people always mouthing off about things because they think it's weird.
But it sounds like your girlfriend is different and won't freak out on you. I know trauma is hard to get past but I think you might be in the clear with her.