15 days late

Has this happened to anyone else before? Definitely not me. I'm regular all the time but I've taken 3 tests now and all BFN. It's been almost a week since I took my last one. I would just like to know if anyone has has this experience? My mom didn't get a positive until she was 8weeks maybe I'm like her? And I have almost every pregnancy synthom. Help please!!!!! Lol crossing my fingers I am :)