How do you know when your period is back?

I’m 2 and a half weeks postpartum and my lochia stopped last week. Now after 5 days or so, I’m bleeding again. It’s bright red and reminds me of my period. I realize that I have no idea how to distinguish when you get your first period again after giving birth versus just residual bleeding. I’m not breastfeeding so I know to expect it to return sooner than later.