8 weeks ago I had my first period, but I still haven't started my second cycle. Is this normal?

Don't worry, this is normal. Since you just started your period a month or so ago, it won't probably won't be completely regular for a while. When I first got my period (I was twelve as well), I went three months without having another one. Everyone's different, but it should start becoming more scheduled in time. If it's still not regular after a long time, then I would ask a motherly figure or your doctor.