Is this normal?

Emily

I took my last pill on 17th July and had my withdrawal bleed from 22nd to 25th July. AF was due again on 19th August but nothing. I've done a PT just in case and that came back with a BFN.

Is this normal?? We're hoping to start trying at the start of next month but I don't know if it'll be worth it because I now don't know when my fertile days will be?!