Your period is over simply when it stops. For some girls, they can have a bit of left over blood leak out a day or so after they think their period is over. I suggest you wear a liner for a couple of days after your period to protect against this. If you spot consistently between one period and the next, see your doctor. Breast size and the time of growth are largely genetic. Ask your mum about her growth through puberty. If you have your periods, they may not grow much more.