New mommy and SCARED

I'm 20 days late had a regular period then they just stop coming I am 5 months postpartum and breastfeed. My husband and I don't have protected sex and we don't practice any type of birth control not a even the pull out method. I have taken 6 hpt home pregnancy tests and everyone of them came back negative. Should I be nervous that I'm pregnant when I took the pregnancy test with my baby girl she was only a faint line so maybe my hgc isn't high enough for a home test.