Why don't guys in college approach me?

Doeeyess
When I was in high school, every year a few guys would hit on me. Now that I'm in college, I only had one guy ask for my number this semester. When I walk to class or am just sitting somewhere on campus, guys just walk by like I'm invisible. There wasn't one guy who looked my way or tried sitting next to me to talk. None. Even guys in my class don't talk to me. It's pretty boring. The point is, being ignored like this on my first year of college makes me feel like I'm ugly. I see couples and guys hanging out with girls so I figured maybe I'm just unattractive to guys there or something. Why do college guys treat me this way?
Why don't guys in college approach me?
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