spotting on letrozole

on 5mg letrezole and on monday i had a mid cycle scan and i had one 14.5 and one 15.5 in each ovary she said i should ovulate wednesday ish my lining was 11 i got a peak on clear blue on tuesday evening but my temps have put me as ovulating tuesday.. so im now 4dpo and i started bleeding today only when i wipe but it's like a light pink/.. what could this be as anyone gone on to have a bfp bleeding after ovulation..