Periods while breastfeeding a 10 month old

I have been ebf since ds was born and he started solids around 5 months. I got my first period when he was 9 months. Now af is 9 days late and I’m frustrated because I’ve been testing, no bfp and I just want to know what’s going on in my body!!!!! I know you can be irregular while bf, but I thought since I didn’t get it for so long, my body was ready to pick up its cycles again... any input? Also, I would like to have another baby soon, so this is extra frustrating.