Sense of emptiness

Lately life has hit me like a ton of bricks. I'm a male that has recently turned 20 years old and I feel as though I really haven't done much in my life, besides having stellar academic grades. My overall self confidence and sense of self worth is at an all time low. I never feel happy anymore and when I do feel happy it's temporary. I've become really depressed that I've only been in one romantic relationship in my whole life, and it only lasted a brief 9 months. I'm starting to feel like my only missing piece in life is a significant other, and I'll feel truly happy and complete when I find that person. But of late it's just become a power struggle to move forward. I've fallen deeply in love with a girl in particular but unfortunately I feel as though they may not love me in the same way. Also there's just so much against the odds between us, even though we share a lot of the same interests and enjoy each other's time, it just seems like it'll never work, which hurts the most. I feel like she's the one, the only one, and if it doesn't work with her I feel as though I'll never find another. I feel not good enough, like I'm cursed, like love and me are not meant to be, even though it's all I ever want in life anymore. I try to stay positive and optimistic but it's so difficult at times, when your mind only thinks in the negative. I feel empty and hollow and don't know if I'll ever feel whole.