Hi, I Passed What Seemed To Be A Flesh Type

Hi, I passed what seemed to be a flesh type thing, almost looking like raw chicken during my lady time today. I have been having my lady time for two weeks now and it is heavier and longer than usual. This is the first time I have bled since I had the injection in June and I had a pregnancy test saying I was not pregnant the same day of the injection. All the out of hours doctor had to say was it is most probably a miscarriage however I highly doubt it is. Is there anything else this could be?