My little sister has a boyfriend and I don't?

My little sister is 15 and I'm 19, but she has a boyfriend and I don't. I've never had not even one boyfriend yet. This just really made me feel bad about myself. The guys I have known were either jerks who just wanted sex or they're nice guys, but I didn't have chemistry with them. And I just don't think it's right to say yes to that nice guy just to say I have a boyfriend, because that wouldn't be good for me or him. I feel undesirable. I get looks when I go out sometimes, but the guys never approach me. I think maybe it's because I'm too shy and look closed off, even though I mostly always have a friendly face. I've been thinking about approaching a guy I thought was cute, but I get so nervous and I kinda believe in the guy chasing the girl old type of thinking. But it seems like guys want you to chase after them now. Ugh I'm just so frustrated :(
My little sister has a boyfriend and I don't?
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