Misscarraige? False negatives?

Patient: Backstory – Nearly 2 weeks ago I started on the Depo Injection. A day after I recieved this i came on my period after being late, I saw two clumps of tissue like stuff during my period. Was this a misscarriage?I then took a pregnancy test just under a week after this, which was negative, would this be a flase negative at all?

Doctor: