No af this month HELP

So last month my period was late by 9 days and I took pregnancy test all came back negative but eventually I started period on 29th of June and it ended July 4th, this month I ovulated maybe on the 13-19, but I don’t have my period today is July 31st, some people say because my last month period is late it caused this period for this month to be missed or pushed in August. I don’t understand please help