12 year old... Need period help / advice?

very normal hun :) the brown discharge is old blood and old residual tissue from the inner lining of the uterus, sometimes the body doesn't flush out everything during your period and when you are about to start again everything reopens up and begins to cleanse itself again beginning with the older stuff. your cycle probably isn't messed up it might just be stress or something but if you think it is then try taking some vitamin B6 and B12. it can help naturally correct your hormone levels that cause your cycle to stay on time, if you don't need it or take to much your body will just get rid of it next time you use the bathroom so no worry about over dosing.