Is It Normal To Have Irregular Period?

Im a 13 yr old girl who is not close to her mom. I started my menstrual cycle and ive had it for about 5 or 6 months now, but its very erratic. the days are never the same - or close in range, really - and sometimes i miss it all together. Ive asked my girlfriends about it and they suggested i just tell my mom, but ive completely ruled that out. A few of them also said their cycles were like that too but not to worry about it. I trust them, but i would rather have reassurance from a doctor that its alright. I am about 5'9 (tall for my age, i know :P) and am very muscular but weigh about 230. It doesnt look like I weigh that much but the scale doesnt lie... hopefully. Thank you very very much xx



medical history: tonsils taken out.

allergies: penicillin