PP period

Madeline

I am now 3 month pp I had my first period in June that lasted 14 days long and it started 28 days after I stopped breast feeding, this time around I’m currently 6 days late on my 28 day cycle, so far it’s almost up to 35 day cycle. I did take a pregnancy test and it appears to be negative. My question is when should I call the doctor to get checked out about my periods? Or what should I do? Any advice?