Every guy likes something different. I know guys who like thick girls and I know guys who wouldn't touch a thick girl with a ten foot pole. Everybody has their own preference. I say try to be the best you can be and don't beat up yourself. If you work out regularly and take care of yourself then at least you'll know you're the best you can possibly be. You'll never know just how good you can look until you work really hard at it.
Don't be one of those girls that complain about guys liking slim girls all while shoving cookies down your throat. I have some friends like that and they annoy the heck out of me. Get up and be the best YOU you can possibly be. If you rarely exercise or you know your eating habits suck then you know for a fact that you do not look as good as you could, and that applies to EVERYONE, slim or not. I am one of those skinny girls that weigh 110 lbs., I am very fit and active, however, my eating habits suck HORRIBLY. Because of my terrible eating, I know that even I could look even better than I do now because your diet does greatly affect how you look. I know firsthand how hard it can be to motivate yourself, but just because something is hard doesn't mean it's impossible ;) Taking care of yourself and being healthy is universally attractive!
In my experience, there is nothing magic about girls who weigh 110 or less, and that all guys are looking for that. If a specific girl happens to weigh that, and a guy is into her, that's great. But I don't think it would be just because she's petite.
Some do. Some don't. For me, it's not about the weight. If she is proportioned the right way, she could weigh whatever and it wouldn't matter. As long as she's healthy. Not long ago I was courting a very petite girl. Her body was a lot thinner than I'd normally like, but other things about her made up for it. There are a lot of factors. There's no clear-cut answer.
You know, I'm all for loving yourself and appreciating the fact that you have curves. But don't put down skinny people in the process. That will just make you look insecure and jealous. It's fine for curvy people to like their curves, as well as it's fine for thinner people to like how they look, AS LONG AS everyone's being nice to each other. There's more to a body than just "meat", you know? There's more to a PERSON than the body he or she has. And most guys realize this. Guys like women of all shapes and sizes, like bubbiexo said. You don't have to be skinny in order to find someone who likes you, and neither do you have to be curvy to be able to attract someone. Learn how to love yourself and learn how to not be so mean to others who are different from you. Then maybe, someone will actually start liking you back.
Guys prefer women of all different shapes and sizes. Some guys like skinny girls, some guys like muscular girls, some guys like fat girls, some guys like curvy girls, some guys like skinny curvy girls... It's not a one size fits all world.