there are definitely guys who like "preppy" girls. there are two types of preps though you have pay attention to your labels girl! lol there is the new breed of like air headed girls who tan constantly and shop at abercrombie and fitch, hollister, and such places. then there are the classic preppy girls who are like generally educated, wear high class labels like ralph lauren, locaste, etc. and have a girly but classic style of dressing, etc. there are guys that like both of them of course. also there are lots of ways of being girly, not just preppy. there are girly emo girls, girly urban girls, etc.
there are also definitely guys who like girls like you. I will say that I have noticed that like girls like you have a tendency to be very lacking in confidence. I don't know if that applies to you...? you might want to work on that. there's nothing wrong with wearing baggy pants if that's what you're into. I don't know what you mean though - as in like baggy jeans or sweat pants? I've worn sweat pants and tank tops to school and I still get attention from guys because of the way I carry myself and my confidence, I'm very flirty, etc. being good looking also helps but that's with anything. I doubt that a gorgeous girl is going to get 0 attention from guys if she dresses the way you do.
you could try to switch your look up every now and then to flatter your body more. I'm not saying you have to like transform to dress the way many of us do but variety is better than just the same thing every day. even switching up baggy jeans for a great fitting pair of bootcut or skinny jeans with a regular plain tank top can drastically improve your look. it shows off your figure more with little effort. everyone wears skinny jeans these days even guys are doing it. lol
i do wear makeup. I love it but I don't wear it all the time. you don't have to. in fact I'm a firm believer in like not changing yourself just for a a guy, but they are visual creatures. so it goes back to confidence and personality. if you aren't good looking then you need one great personality to reel them in. flirting never killed anyone either ! :D
also you mean big sports jerseys? and baggy jeans? what are you trying to hide girl goodness. I've known tomboys who don't go out of their way to cover up their body, so I don't think not being girly is like your only prob here. I've seen tomboys wear shorts, tank tops, regular tees, regular jeans, etc. it sounds like you are insecure. I could be wrong but if you are actually going out of your way to cover up then you are insecure and that most likely trickles down to your personality as well. good luck! :)