What Causes Vaginal Bleeding After Intercourse?

i have irregular periods and 2 days after unprotected intercourse i went to the bathroom and when i wiped there was a small amount of blood/mucus discharge and that only happened once and about 4 days later when i go to the bathroom theres a brownish discharge so i'm confused it's now been 3 days since the brownish discharge was that just a light period or could that have been implantation bleeding?