Gestational diabetes???

I am just wondering about that test, when do you get tested for it I'm 16 weeks pregnant and at the last appt my dr asked me a bunch of questions of ya know if any diseases or abnormalities run in either of our familys and well to be honest diabetes like majorly runs in both of our families and well I am really scared I might end up with it, i am scared of needles I would die if I had to give myself a shot everyday, would my dr. know by any of those other blood tests I have gotten if I have it or not or do I have to wait to have the gestational diabetes test done. when will I get that test???