What should I do about my family?

See, my parents are both relatively accepting (but my dad resents me a little because he might not have grandkids and he was raised catholic) and my twin sister completely hates me but im ok because we never really liked each other, now she just has a stupid reason. The problem is coming out, see I'm biual- borderline , and I've told my family and my 10 closest friends and a few other friends who I trust. But I want to find a boyfriend, I'm 15 and I'd like to have a same relationship before college so I'm ready for relationships later on, and I think being with a guy would make me happy. I don't know any gay or bi teens my age and my parents don't want anyone to know I like guys so I already went behind their backs, and they definately don't want me dating a guy until later on. What do I do? How can I convince them to let me be a little more open about my uality and maybe find a guy to be with? I want to be myself but they don't think I'm ready, hell I've known who I am for at least a year and now some of my friends do, why can't I be with who I want?