Ovidrel

Not sure what to think here ladies.. I did the ovidrel shot on 8/14 so today is 15 days past trigger and 13dpo. For the last 3 days I have been getting extremely faint lines. They aren’t getting lighter but also not any darker. Think it could still be the shot? Or maybe a bfp starting? My period is due sun/mon. I just don’t want to get to excited.. Any advice would be great.