I'm a seventeen year old guy and I feel like I'm invisible

Every time I've ever tried to talk about this to someone I care about they've left, but I guess the point of this is to be able to say things you wouldn't normally.

I've always known I was nothing special since I was little. My family had an unhealthy dynamic and they were verbally abusive. To them, you were either talented or you were worthless, and that made me worthless to them since the earliest I can remember. My sister got all the special treatment growing up, and my parents just look at me like I'm this massive failure. In school I never got picked for anything, and nobody has really paid any attention to me. I haven't had a problem with it until recently when a girl asked me on a date. We dated for about a year, and I guess we were pretty serious, but she just left me last week. Over the course of the past few days she hasn't even looked my way, and that's when I realized that nobody does. Not a single soul wants to look at me, or talk to me, or as far as I'm concerned, even think about me. There are about 3 or 4 people that I've known for a couple years, and they'll talk to me occasionally but I could still disappear for months and they don't even notice. I just wish that I had even one person I could call a friend, but I'm awfully average. And I have this paralyzing fear coming over me because I'm only about to leave high school, and everybody notices everything in high school. It's such a small world there, but what's going to happen to me when I graduate. The world's just going to get bigger and I'll be forgotten. My family will kick me out, stop talking to me, and all the people I know will move on and leave me behind. I just don't want to be forgotten.