"old blood" for 9 days??

So I hope I'm doing this right, I rarely ever post on here but I really need help. So my period has never done this before which is why I'm so worried. So today is March 10th, and I "started" my period on March 1st. It's only been old brown blood for the last 9 days. And its barely any at all, it's the equivalent of light discharge, but it's brown old period blood. For reference, I'm 17, started my period at 15 almost 16, my period is usually moderately heavy and lasts 4-5 days. I don't have insurance so I can't just up and go to the gyno just yet but I'm just super worried. I'm not sexually active so it can't be anything relating to pregnancy. Am I worrying for nothing? Is this just a thing that happens sometimes?