?? Help

So the 19th of March was the last day I had protected sex. With my knowledge I know the condom didn't break either time we did it.  Both this app and my other calendar say I am due today but I'm having brown discharge (very little amount). Do you think it's possible that it's from my last period? Or is it implantation bleeding even though I'm due for my period today, Which was a week early last month. Sorry. I'm just super paranoid and really don't want to be pregnant.