What Causes Brown Spotting And Irregular Mild Bleeding Post Childbirth?

Just wondering if I should schedule an emergency appointment.. I have an almost 6 month old infant. Had a period the first 3months after birth. After 2 months of no period and 2 weeks of horrible migraines small cramping that came n went with no pain and mood swings, I finally started spotting a week before I would normally have my period. It was only when I wiped for about 4 days.. I had intercourse and it went from just wiping to light bleeding filling maybe 2 panty liners max for 5 days only if I pushed myself. I usually have clotty heavier periods using a couple super tampons a day.. Today being day 6 its now back at brown and hardly anything.. Everything on Google says implantation bleeding I ve taken a test while still bleeding and it was negative I ve also ruled out eptopic pregnancy BC I have no severe pain an the negative test.. Advice please?