What Causes An Irregular Menstruation?

Hi... I'm 20 .I always have an irregular menstruation cycle. Probably caused of genetic problem. Because my mom told me that my dad sisters always have the same case as me. But in the last 2 month, my menstruation start to be more regular, although since last month, it hasn't stopped up to now. But it's not a lot. It's a little and brown color mucus. Is it OK? I thought that probably I'm too stress or something.. But is it normal?
PS: I haven't done sex..

THank you..