What Causes Spot Bleeding And Brown Spotting After Sex?

i,ve had a mirena for 2 years now, at the time of insertion i had womb biopsies taken which came back normal. my problem is i am now experiencing spot bleeding and brown discharge that flares up a few days after having sex, i had a loop diathermy in 1993 for cin2 iam now 43 , i have a pap smear booked for tomorrow and a scan in four weeks i am very worried about cancer, please advise