When's puberty going to kick in?

Ok, I've asked this same question months ago, and since then, nothing has happened! I'm a teenage girl and my period hasn't even started yet! I'm still wearing "Training bras" but I'm completely flat chested! During gymnastics, girls are asking me for tampons and I always feel left out because I don't have any to give them! I hardly even smell afterwords! I asked my doctor what's wrong, but he said it will come over time. Is something wrong with my uterus or is it just me? Geez, why can't I be normal like everyone else?