I don't think it's selfish. You feel what you feel- and loneliness is such a strong emotional feeling. It can creep up any time. And it's so sad when the feeling lasts for a long time.

College was a terribly lonely time for me. I didn't really help the situation, I never reached out. I was a total workaholic and drove myself to awful loneliness, anxiety, and depression. I made some very good work, I excelled, and I landed a job immediately after graduating. But I wish college was a happy memory. I don't regret working hard, but I hate that I wouldn't fix my isolation.

A big problem with the pain of loneliness is it can confuse you into thinking that you are a loser, an outcast. I really do take your word that you are working hard on your character and health, I did that after school ended. So don't begin to think there are some hidden flaws you can't see. Loneliness is a feeling. And a strong one when directed romantically.

I don't know what I would've done in college to fix myself, but I know what helped after graduating was to focus on the needs and feelings of others, and less attention on my own lonely thoughts. Kindness goes a long way.

I don't know your situation, whether high school, college, post-grad, or even middle age. But there's always somewhere to focus on others, even if it's intimidating or you don't feel worthy. In high school I did programs at the library helping little kids after school. Just basic reading and stuff. At home there were always ways to help out. After college when I tried to settle in a city I went to a food pantry once a week to help organize the donated goods. I was too shy to serve at a kitchen, but behind the scenes work was important. I never joined school programs, but if you ARE in school it could help you to find one to join. As far as romantic interests go, some people swear by online dating sites. I never used them out of not wanting to go through bad matches or bad dates. But you never know what'll happen.

Anyway, different stuff works for different people. And you may not have the accessible opportunities like I did. But taking your thoughts out toward something else is a great thing. Even just picking up a new book and losing yourself. Organizing your space and de-clutter. Just remember like I said that loneliness is a feeling. Anyone can get it, and it doesn't mean you lack character or are undesirable :)