At this resturant me and my family went to this group of college guys kept staring at me and I heard one of them say "oh she's looking at you". Guys at my high school stare too. I don't wear anything flashy and I'm not a loud person. The funny thing is they don't rarely talk to me but they talk to other girls so I don't think its cause they like me. It makes me feel so self concious!!!
Guys stare at girls because we (humans) are visual creatures. We will look at anything we find attractive. Same with girls. They just just did it shamelessly. Most people would be discreet about it. I wouldn't worry too much about it. It's going to happen a bunch in your life, whether or not you think you're attractive or not.
Do you have a big butt? Other large... appendages? If you do then I GUARANTEE that's what it is. I say own it unless it makes you uncomfortable, and in that case just tell them to keep their fucking eyes to themselves