Period after first pp period

Alissa
I had my first pp period July 17th and it lasted 6 days.  I had gone 5 months without one. Well now it's been 40 days since that period.. My normal cycle before baby was usually 30 days long. So  10 days late. I have taken 4 pregnancy test over the last 10 days and I'm not pregnant. I understand having a baby can change your cycle but anyone else experience something like this? Hubby and I would like to start trying for baby #2 real soon but I need my period so I can start hunting down my ovulation!