Mine didn't become normal until I got on birth control. I could easily go 6 months without a period. Which was nice but never knowing when to expect it was not so nice.

FYI, most guns won't shove a speculum up a 13 yr old if there's any way they can avoid it. They will sooner do extensive questioning about the symptoms.

I would not take my kid to the doctor for what you described - she's in the range of normal.