what can cause pale pink discharge mid cycle?

Shelby

it happened last week. it was the palest shade of pink, light barely noticeable and only when i wiped once. i had an ultrasound later that day and the doctor said it looked like i haven’t ovulated in awhile (i have PCOS) so what else could have caused that? i assume i’m not pregnant since he said that. af is a day late so far.