Pregnant?

ka

I usually get my period the 15-17th, last month was normal. This month I started the 1st-6th, supposedly on app I ovulated the 14-15, so today it says I’d be 7dpo. I’ve had cravings, headaches,backaches,mood swings, crying spells. Yesterday test was BFN. How long until I know WHEN TO STOP TESTING? Or what day to correctly test on? Could I be pregnant ?