I never had regular periods except while on the pill. Mine started at age 13 and they'd be anything between 28 days and 3 months apart. Of course, I haven't gotten it back since having my ds yet, maybe when they come back they'll be regular (crossing fingers). So, it can be pretty normal for some. I've never had a gyn think anything of it. ETA: I'll be 20 in 2 weeks.