Am I normal. I want your real answer please not what everyone says. Even if its bad. Lady's only. About period?

I have not started my period and am 12. I have small but I am a small person. This is sorta 2 questions in one. I weigh 29 kg and am 148 cm tall. Does this effect my late starting in periods? My friends say i am thin but I think im fat they say this is why i haven't started. I have white stuff in my underwear every day for about 14 months but am not sure if this is just an infection. I found lots in my pj's this mournig and regulaly have stomach aches/mood swings. Am I just overreacting or am I actualy starting my period like all my friends have allready. Allso am i underweight?