Ok I know of 2 people that it happened to...........

A girl I work with didn't find out till she was 3months along.She had suspected but the hpt she was doing kept coming up negative!Also she had a b/t at the doc's and that came up negative...but 2 months later....a positive.

A friend of a friend didn't know she was pregnant, she was 7 months along and just didn't realise.Apparently her periods were irregular and she never guessed she'd be pregnant!