What does this mean?

So I overthink sex a lot like I’m a virgin I’ve never done it. for some reason whenever I think about sex it makes me feel really dirty and disgusting and whenever my friends talk about it or I hear someone talking about it I will literally think about it for hours obsessing over it wether it’s nasty or not and it makes me feel differently about my friends like their dirty and sluts. I know it’s not a bad thing but my mind automatically tells me it is and that’s why I’ve never had sex because I’m scared that after it I will feel disgusting and hate myself for it. What could this mean? I’m 19 btw