Why was he staring at my butt if it’s not big?

There’s this guy in my class he’s always looking at me. today when I had signing myself out to use the bathroom I was standing in front of him. I could feel him stare at my butt for like the longest time ever. My question is why I don’t think I have a very big butt I would say it’s more in between but I wear a lot of loose clothing such as pants cause I have scoliosis and sometimes skinny jeans hurt me from my waist. So my question why was he staring at me?
Why was he staring at my butt if it’s not big?
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