Is it normal to only look "hot" with certain clothing?

I know this might seem really obvious but I have just been noticing something.

Wake up. Find something to wear. I decide to wear a nice outfit. Something that still covers my boobs and butt (amazing right?). I go to school and I notice some guys that usually don't ever look at me, looking at me. They give me a certain look that I would associate with oh I don't know, arousal of some sort? And the guys I sometimes talk to, talk to me with more smiling and more flirtatious body language.

This happens when I wear certain outfits. All of the outfits cover my areas well (no cleavage, no butt cracks) and don't show much skin at all. One is even long sleeved. I wear long jeans with most of them except one with capris. (Short shorts are just...no.) Another is a dress that is long sleeved, length to my knees, and I even wore opaque tights with it.

As silly as this sounds, I just don't understand why guys look at me differently when I wear these certain outfits. From the media, men like women who wear clothes with their boobs out, short dresses, whatever. But of course, real life isn't the media.

Maybe some of you could describe certain clothing you find more attractive on women?
It just doesn't make sense because I don't feel as though the outfits are "sexy", compared to what I've seen on other girls. So why do I feel that guys seem to give me more attention when I wear these clothes? It's as if I'm only attractive when I wear these outfits. If I decide to wear a baggy sweater, I'm basically nobody in terms of attractiveness.

Do you find girls attractive only if they decide to dress a little nicer that day? Because that's what I've noticed from my experience.