Concerned or??

So I’m 3 months post partum. I started birth control and my first post partum period on January 2nd, it didn’t end until January 29th. My husband and I had sex that night. Since then I have not gotten my period again, it’s only been 2 weeks but this app says I should’ve gotten it yesterday. I’ve been cramping a ton for the past week in my lower back and typical period cramps, but no bleeding. As much as I love my little baby, I DO NOT want another this soon. Should I take a test or wait it out a little longer?