Why do guys just use me for sex (NSFW?)

I make it so clear that I want a relationship and that I don’t want to be used for sex. Never got any sort of disagreement or anything so I figured they were looking for the same thing. Turns out they aren’t and they just took advantage of me and used me for sex. Now I get ghosted and I feel like shit for allowing myself to be used. I just want to feel safe and happy. I don’t even know why he ghosted me like I was nice to him and all that. But I guess it doesn’t matter, I’ve never been on a date with a guy or anything, despite “dating” a guy for 2 years.. I always just get used for sex.