Say in high school you were a very popular person. Whether you were a cheerleader at your high school or grew up with 90% of the student body, at one point you were popular. Those four years were most likely the best four years of your life. But now you're in college and the tables have turned.
This isn't required-schooling-lets-band-together type friends anymore. People are here to get degrees, to develop their future. Maybe because everything is different than high school it's harder for you to make friends. So your first semester goes by and you have one, maybe two friends if you didn't immediately rush for a fraternity or sorority and or join a club or a sport. You hope next semester all of the sudden you will gain that popularity again. Be able to know everyone that you see between classes and in them. Second semester rolls around. Now it's three or four friends and you think you're slowly getting there. But your self-confidence takes a big hit. You're in a different place with different people and you don't know what to do.
Popularity not found. Error. Error. You worry about what is wrong with you.
There is a lie about popularity, it hardly ever exists in a pure way. I knew my entire senior class and most of them knew me. But they didn't know where I lived or have ever seen my stuffed bunny. They might know what classes I take and what sports I play but they don't know how my nightly routine after I get home from practice. I only had a few true friends and best friends that know the name of my dog that past, what college I'm attending off the top of their head and know how frustrated I get when my feet are cold. I now have friends here at college that know those same things. I may only know a handful of people here and only have three or four friends but I'd rather cherish those friendships than have everyone know me by my face or that I'm in their English class.
If you were popular in high school, it doesn't mean that you're any less of the person you were before if you're not popular in college. What college boils down to is your future. You're ultimately there for your future, whether you know it or not. You'll find your lifelong friends, your maid of honor, your best man, maybe even your best friend. Either way, popularity is a scam and basing self-worth on how many people you know and how many people know you will come up with an error code.