I Feel Very Unloved

I know it's normal and that people usually find love later in life, but I just feel so sad most of the time. Why didn't I find my other half yet? I'm almost 20 years old. My own mother needed 16 years to finally show some affection towards me (I'm her biological child), she only said I never asked for love before.
It almost breaks my heart when I see all the happy couples around. I'm happy for them, I really am. But I can not wonder, why couldn't I be happy with someone? It's not that I didn't try, I just can't be with someone I don't see as anything closer than a friend. And it's unfair to be with someone who has feelings for you but you know you can't reciprocate.