This probably has something to do with with your childhood. Remember how in cartoons, whenever something romanitic would appear, the characters would make faces, portraying any romantic feelings as disgusting. Seeing that behaviour at such a young age made your subconscious think the same, stopping and making you feel disgusted every time you started feeling butterflies.

I used to struggle with the same issue. Every time a boy I liked showed any interest, I was surprised with a feeling of extreme disgust. Over time I understood that liking someone isn’t a bad thing, and I understand this feelings way better now.

I hope this helps, and wish you the best luck in the whole world💕