Stories of delayed BFP's?

Hey ladies, do you have any stories from either your experience or someone you know who knew they were pregnant but couldn't get a positive?

Just for fun and curiosity sake!

My mum actually had this happen to her when she was 18. She said she knew she was pregnant the whole time but couldn't get a + until 10 or 11 weeks! U/S confirmed she was right about the dates.