You are just 12yrs old and cycle starts one month ago.
Basically it takes 6 months to 2 yrs for getting regular period after attaining puberty
. It is due to anovular cycle.
Take healthy diet including low salt,maintain personal hygiene, sleep well and meditate sometimes ....all these help to improve your health.
or lower abdominal pain
is more then take Tab Ponstan
500mg BD or sos.
All the best.