Still no period!

I was set to start my period the 4 of this month & here it is, the 13tg & no period.

I took a pregnancy test the day I missed & then 4 days after I missed. Both said negative. I just had a baby 8 months ago. & I’m kinda terrified that I may be pregnant and I’m just to early to tell on a test?!

Thoughts? Could I be? My period hasn’t been late since I had my daughter. And no I’m not on birth control. What should I do? Wait another week? Then retest? So many questions!