Why do guys, if they talk to me, only want sex?

Now, I am not a guy, so I can't speak to their thoughts. Even if I was a guy, I couldn't speak for everyone.

That said, there seems to be a certain mindset that men and women are entirely different and will never relate to each other outside of romantic entanglements. We seem to be taught that the opposite gender is mystifying and we will never understand each other.

There is also the idea that 'manly guys' can't express emotion/be romantic. They are 'rewarded' for having sex, and told by movies that that's just what guys do.

The final thing to note is something that I think was said best here:

The sun isn’t bright just because I say it is. It just is. It was bright before I even knew the word for bright. I didn’t decide what it is, I acknowledged what it is.You aren’t worth something just because I say you are. You just are. You were worth something before I even said anything. I didn’t decide that you are, I acknowledged that you are.This is what I mean when I say “You are worth it.”

I'm going to be blunt here: there's a section of the male population that will home in on women who're shy or have lower self esteem (which it sounds like you may have regarding your appearance/desirabilty) because they make easier targets. Since they're specifically just looking for people to have sex with and will be glad just to have someone show interest, getting those guys to care about anything more is a lost cause.
One of my female friends had this exact problem, and I'll tell you what I told her: stop sleeping with these assholes. Find someone who you like, or likes you, and build at least a bit of a relationship first. There's nothing inherently wrong with diving into bed with someone you're interested in, but for people in your position it usually isn't what you want, and settling will just end up hurting.
If you want to talk in-depth, feel free to message me. I can be more specific/helpful if I know more about you.

Hey! hey im a guy i kinda felt offended by that lololol jkjk even I have to admit MOST guys think with something else and it not their brain BUT not all guys are like that some guys truly believes that sex ain't better than love and will get to understand you and not all of us are bad . You just got to come across the right guy :) but yes unfortunately females are always at a disadvantage when it comes to relationships not working out you have my sympathy but that's not something you or I could change. You just gotta find the right nice guy that likes you for who you are :) I wish you good luck

well, i cant truly awnser that question without knowing your life, to be honest you might have gotten to the point where you have assumed that is what some guys wanted and didnt respond to them, but again i have absolutely no idea. but i can cange the trend, im a guy, want a friend? just send me a message at any time ^_^