Dude, I feel you so much. Although I'm probably much younger than you [3rd year CS/Physics double majoring], I'm in the exact same situation; no girl considers me, never had a gf. But honestly, from my own experience, find a thing you love. Just do something that you love so much, you feel like you never want to stop. For me, it's research. I love research and I love meddling with the innards of the world we live in. I strongly suggest you find a similar hobby/thing you love. Then obviously hit the gym [if you haven't already], you'll feel so much better, trust me on this. And honestly, if you are independent, if you begin to love your life and the stuff you do, you'll kind of forget about this whole concept of 'no gf' and such, and as time comes, the girl will come to you ;) Perhaps girls find you 'out of their league', or perhaps they think you're already taken. If you're really having self-issues due to the fact that you've got no gf I strongly suggest you to read 'the game', it's an excellent book.

Good luck brother!