Need advice!

Not even 2 weeks after period I am now bleeding brown to dark red with clots. With back pain and stomach pain. Could this be a miscarriage or conceiving? Has anyone ever experienced this type of pain that's not a period? My partner and I had intercourse a week after my period. Had 2 negative tests but in my family it takes up to 8 weeks to show up on a test. Any thoughts? Very appreciated thanks!