i'm 24, and i'm no stranger to irregularity with my periods, but they've always been ... "consistent" in that if i was heavier/lighter than normal, lasted X amount of days than normal, etc., i could usually attribute that to being irregular.
however, within the last year or so, my cycle has been incredibly weird and really light. sometimes i'll have it for two days, disappear, and reappear on the fourth day and then i'm done with that cycle; sometimes i'll have it twice a month but a similar pattern will occur where i might have it for a day and it'll come back three days later, etc. - and all this time it's really light bleeding. and then there are other times, like this month, where i won't have it at all. i had my last period earlier in late february/early march, but it barely lasted a day.
and no, i've never had sex and, as far as i know, am rather healthy. i did talk to my friend about this, and she seemed to think that it was a little odd but that i was also overreacting. if it sounds like it might be really serious, i'll consider seeing a gyno, but it's an option that wouldn't be feasible right now unless it's an urgent matter.
i feel like this should be common sense, and i apologize if i sound really uneducated about this. it doesn't really bother me, but i am curious as to what might be causing this.