Early and long period...implantation?

So I never get my period early but this month it came 3 days early and so far has lasted 8 days. It never lasts more than 5. It started out light then turned to a brown color and my vag started having a burning feeling too. There were 3 days of just super watery heavy bleeding. Now its just light but won't stop.... Any ideas? Could it be implantation bleeding? Should I test? Can I test while I'm still bleeding?