Can implantation bleeding last as long as a period?

I doubt it: Theoretically yes, but most 'implantation bleeding' is really breakthrough. 'implantation bleeding' is subtle and unpredictable, if it can be interpreted at all. Internet vastly over-emphasizes the idea. Implantation happens 6-7 days after fertilization, so that's the only time you'd see it. You don't say when your last period was or when you expect your next one, that could help.