BFN 7 days DPO

Really feel like I'm pregnant, but I just got a BFN. I'm only 7 DPO, could I still be pregnant? I'm still confused because I have a short cycle (25 days) and according to the app my fertile window starts two days after my period ends. I know this is a lot sooner than most people.. DH and I dtd on the day before O according to app.. Help!