My Secret Artistic Side and My Fiancé's Jealousy

I’ve been engaged to Sarah for two years now. We met in college when we were both in our early twenties, and we hit it off right away. Sarah is an all-around great person, but she’s never understood my artistic side. I was a painter before we even knew each other. It’s always been more than just a hobby, it’s my soul, really. When we first started dating, everything was fine because I kept my art separate from our relationship. As time passed though, I found myself wanting to show her my work more and more. We moved in together last year after she graduated with an engineering degree, which seemed like the perfect chance to finally bridge that gap between us. But Sarah hasn’t liked it one bit. Every time we visit a museum or gallery, she pretends she’s there out of politeness for me but clearly isn’t into it. She never comments on my work either way, just looks at them as if they’re some foreign language she can’t read and doesn’t care to learn. I know deep down I shouldn’t expect her to love what I do, but seeing how dismissive she is has been hurting me deeply. One night about six months ago, we were sitting in our living room with my paintings all around us, and I broke down telling her how much it pains me that she doesn’t appreciate this side of me. Her reaction was unexpected though. She confessed she had caught me looking at some fan art of a certain fictional character online late one night when I thought she was sleeping, really explicit stuff too. I was embarrassed but also couldn’t deny it, I do sometimes enjoy imagining my characters in different, more sexual contexts, even if they’re just that for myself. Sarah told me she felt like my paintings were an open secret about who I am as a person, while the fan art made her feel blindsided and betrayed. She asked me to stop looking at it so much but couldn’t say whether she wanted me to stop creating or just hide it better from our home life. I’ve tried talking it out with her since then and have even offered to start locking my private work in a drawer, keeping only the more tame pieces out. We’re still together, but there’s this tension now that wasn’t there before. I feel like my identity is split between two worlds, one she knows me as, and one she doesn’t, and it’s killing me inside. I’m sharing this because... well, I don’t know what else to do with these feelings. Maybe someone can relate? Or maybe just putting this out there helps take a burden off of my shoulders.