My length is super-light... why?

So I'm 16, and even though I've been have my period since I be 13, they still haven't regulated. I usually only take one every 2-4 months, and when I do it's really really light. Like a few days ago i saw a bit of red so I've be wearing pads, but after that tiny glow only a bit has in actuality come out.. This is often the skin. Am I excersizing too much? (I run for about 30 minutes a day) Am I too overweight? (5'1, 103 lbs) I'm sooo confused..
Answers:

Could u loose ur viginity with one and the same sex?

your not fat you may not enjoy regulated yet you hae to see a doctor if your worried sometims if you hold light period it can aslo have to do inheritance

What does it means when you enjoy Keytones in your urine?

no your purely one of the lucky few

Nipples enquiry, pls oblige.?

when I read the ? I thought I wish I be that lucky. Now that I see your age it is normal not to be regular surrounded by teen years. Girl don't knock it some of us have the contrasting problem if one could call it that.