Need help....

So I am 4 months postpartum. First time mom. My periods have always been regular even after baby.  my period has never been late until now was due 4 days ago. With no sings of it coming. I don't know what to do.  I am on the pill I missed a few days tho. My discharge is creamy wight and sticky. Is this normal? I tested two days ago and it was negative. I really don't know what to do any help is appreciated.