Possible miscarriage

I should be about 5 weeks when I passed this unknown tissue last week. This happened little over a week before my period was due and it was heavier and brighter than normal. Lower back ache, my boobs are tender, I was very tired. I also never passion tissue with my period. Had cramping ever since I supposedly conceived. I never had a positive pregnancy test so I'm thinking it was a chemical. Bleeding last about 2 days and lightened up after basically a gush of blood and then this later. Has anyone ever seen anything like this??