Late period... BFN

Courtney • I`m 27 and married for 7 years.. Baby #1 born April 2013, Baby #2 born December 2014, and Baby #3 born June 2017 and due July 2019 with baby #4 :)

So I’m almost 5 months postpartum (baby #3)

had my first postpartum period September 18th after a chemical pregnancy (baby #4). My next period was due October 19th and it still hasn’t came . I spotted for a few days starting October 5th but that was it. I have taken a few pregnancy tests and all have been negative. What’s going on??